Ethereum Glossary: How ETH, Gas and Smart Contracts Work

Use this glossary as a map rather than a list to memorise. Start with ETH and the Ethereum network, follow the path through an address and a signed transaction, then see how gas pays for execution and how a transaction hash reveals the result. This sequence helps you understand what a wallet is asking you to approve before you transfer ETH or interact with a smart contract.

Essential Ethereum glossary

Ethereum

Exact meaning: A blockchain network designed to record transactions and execute programmable applications. In plain English: It is a shared computing and record-keeping environment operated under common protocol rules. Where you see it: Wallet network selectors, exchange withdrawal forms, application documentation and blockchain explorers. Decision affected: You must confirm that the sender and recipient support the same Ethereum network before moving an asset.

Blockchain

Exact meaning: A replicated ledger in which transactions and resulting state changes are grouped into blocks and verified by network participants. In plain English: It is the public record that shows what happened to balances and smart contracts. Where you see it: Explorer pages listing blocks, addresses, transactions and contract activity. Decision affected: Check the blockchain record instead of relying only on a wallet notification or screenshot.

Ether and ETH

Exact meaning: Ether is Ethereum’s native cryptocurrency; ETH is its common ticker. It is used to transfer value and pay for computation on Ethereum. In plain English: ETH is both an asset you can send and the network’s standard payment asset for gas. Where you see it: Wallet balances, transaction values, gas estimates and exchange directions. Decision affected: Keep enough ETH available for network fees when an operation requires you to pay gas. Ether can be represented in smaller units: wei is the smallest unit, while gas prices are often displayed in gwei. ^[1]

Coin

Exact meaning: A cryptocurrency native to its own blockchain. In plain English: ETH belongs directly to Ethereum’s protocol rather than being issued by a separate smart contract. Where you see it: Asset descriptions, wallet balances and network-fee notices. Decision affected: Do not assume that every asset shown in an Ethereum wallet is ETH or can pay Ethereum gas.

Token

Exact meaning: An asset whose balances and transfer rules are managed by a smart contract on a blockchain. In plain English: An Ethereum token uses Ethereum infrastructure but is not the network’s native coin. Where you see it: Contract addresses, token balance sections, approval requests and token-transfer records. Decision affected: Verify the token’s contract address and network, not just its name or ticker, before receiving or exchanging it.

Ethereum address

Exact meaning: An identifier for an Ethereum account, normally displayed as a hexadecimal string beginning with 0x. The address may represent a user-controlled account or a smart-contract account. In plain English: It is the destination used to receive ETH, tokens or a request to execute contract code. Where you see it: Wallet receive screens, withdrawal forms, explorer searches and contract documentation. Decision affected: Compare the full address through a trusted channel; matching only its first or last few characters is not a sufficient security check. Ethereum distinguishes externally owned accounts controlled by private keys from contract accounts controlled by code. ^[2]

Private key

Exact meaning: Secret cryptographic data used to authorise actions from a user-controlled account by signing transactions. In plain English: Whoever controls the private key can generally control the associated account. Where you see it: Normally nowhere during routine use; legitimate recipients and exchange forms do not need it. Decision affected: Never enter a private key into a website, message, support chat or transaction form.

Seed phrase

Exact meaning: A recovery secret from which a compatible wallet can derive private keys and addresses. In plain English: It may restore control over an entire wallet, not merely confirm one transfer. Where you see it: Wallet creation and recovery procedures. Decision affected: Keep it offline and private; a prompt asking for it merely to connect, receive funds, unlock a transfer or obtain support is a strong phishing warning.

Transaction

Exact meaning: A cryptographically signed instruction that requests a change to Ethereum’s state. It may transfer ETH, deploy a contract or call a function on an existing contract. In plain English: It tells the network what the sender has authorised. Where you see it: Wallet confirmation screens, pending-activity lists and blockchain explorers. Decision affected: Review the destination, network, value, requested contract action and estimated cost before signing. Ethereum transactions must be broadcast and included in a validated block before their state change is recorded. ^[3]

Smart contract

Exact meaning: Code and persistent data deployed at an address on Ethereum and executed according to predefined functions. In plain English: It is a program on the blockchain that responds to transactions. Where you see it: Token transfers, decentralised applications, swaps, approvals and contract pages in explorers. Decision affected: Confirm which contract and function you are authorising; a familiar-looking website does not prove that the underlying contract is genuine or safe. Smart contracts reside at Ethereum addresses, and state-changing interactions are generally irreversible after execution. ^[4]

EVM

Exact meaning: The Ethereum Virtual Machine, the execution environment whose rules determine how transaction and smart-contract operations change network state. In plain English: It is the standardised engine used to run Ethereum contract code. Where you see it: Developer documentation and descriptions of EVM-compatible networks. Decision affected: Do not interpret “EVM-compatible” as meaning “the Ethereum network”; separate networks may use similar address formats while maintaining different ledgers, assets and fees. ^[5]

Gas

Exact meaning: The unit used to measure the computational effort required to process Ethereum operations. In plain English: More work for the network generally consumes more gas. Where you see it: Wallet estimates, transaction details and smart-contract documentation. Decision affected: Distinguish the amount of gas an action may consume from the price charged per gas unit. A contract interaction can require more gas than a simple ETH transfer because it may execute multiple computational steps. ^[1]

Gas limit

Exact meaning: The maximum number of gas units a transaction is permitted to consume. In plain English: It sets a ceiling on computational work, not necessarily the final amount used. Where you see it: Advanced wallet settings and explorer transaction data. Decision affected: Arbitrarily lowering the limit can make execution fail; unused gas within the limit is not treated as work performed. If execution runs out of gas, state changes are reverted, but gas spent on the attempted computation can still be consumed. ^[1]

Network fee

Exact meaning: The ETH paid for the gas consumed by a transaction at the applicable price per gas unit. In plain English: Gas measures the work, while the fee is what that work costs. Where you see it: Wallet transaction previews and explorer receipts. Decision affected: Compare the fee with the action being authorised and remember that a failed on-chain execution may still incur a fee. Gas fees on Ethereum are paid in ETH. ^[1]

Transaction hash or txid

Exact meaning: A cryptographic identifier generated for a submitted transaction. In plain English: It is the reference used to locate that particular on-chain instruction. Where you see it: Wallet history, exchange transfer records and explorer search fields. Decision affected: Use the hash to verify the network, sender, recipient, status, value and fee rather than treating the hash itself as proof of success. ^[3]

Confirmation and finality

Exact meaning: Confirmation begins when a transaction is included in a valid block; stronger settlement assurance develops as the block progresses toward finality under Ethereum’s consensus rules. In plain English: “Submitted,” “included” and “finalised” describe different stages. Where you see it: Explorer status information and deposit-processing notices. Decision affected: Do not assume that a pending transaction has completed, and check the receiving service’s current crediting requirements instead of relying on a universal confirmation count. ^[3]

Connection map: how the parts form one process

The core relationship can be read as:

Object → network environment → authorised action → block inclusion → verifiable result

1. Object: You select ETH or an Ethereum-based token. For a token, the contract address is part of the asset’s identity.
2. Network or environment: You select Ethereum or another explicitly supported network. Similar address formats do not make networks interchangeable.
3. Action: A user-controlled account signs a transaction. A simple transaction may transfer ETH; a contract transaction may transfer a token, approve spending or execute another function.
4. Execution cost: The operation consumes gas. The resulting network fee is normally paid in ETH on Ethereum, although some application designs may sponsor fees for users.
5. Confirmation: The transaction is broadcast, enters the pending pool and must be selected for inclusion in a block.
6. Verifiable result: A blockchain explorer can locate the txid and display whether the transaction succeeded, failed or remains pending, together with its addresses, value and fee data.

A read-only contract query does not change blockchain state and can be performed without creating an on-chain transaction. Writing data—such as transferring a token or executing a swap—changes state and ordinarily requires a signed transaction and gas. ^[6]

Do not confuse these Ethereum terms

ETH and an Ethereum token

ETH is the native coin of Ethereum and is used to pay ordinary Ethereum gas fees. A token is managed by a smart contract. Receiving a token does not necessarily mean the same wallet has enough ETH to send that token later. The practical consequence is a stranded balance: the token may be present, but the account cannot authorise an on-chain transfer because it lacks the fee asset.

Asset and network

The asset answers “what is being transferred?” The network answers “which blockchain will record the transfer?” ETH can also appear in representations or environments outside Ethereum, and many token tickers exist on multiple networks. Choosing a destination address without verifying the supported network can result in delayed recovery procedures or permanent loss.

Gas and network fee

Gas is a measurement of computation. The network fee is the amount paid for that computation. A high gas limit does not by itself state the final charge, and a low displayed price per gas unit does not mean a complex contract call will be cheap. Check both the expected gas consumption and the fee estimate shown before signing.

Transaction value and transaction fee

The value is the ETH sent to the recipient or contract. The fee is paid for processing the instruction. A wallet balance must cover the intended value plus the possible fee. For token operations, the token amount and the ETH gas balance are separate.

Wallet address and smart-contract address

Both may use the same 0x-style format. A user address is controlled through keys, while a contract address contains executable code. Sending an asset directly to a contract that was not designed to receive or credit that transfer may make the funds inaccessible. Identify the intended recipient type and follow the receiving service’s deposit instructions.

Seed phrase and private key

A private key controls a particular derived account. A seed phrase may recreate many keys and accounts within a wallet. Exposing either is dangerous, but exposing the seed phrase can compromise a wider set of addresses. Neither secret is required for someone to send assets to you or verify an on-chain transaction.

Transaction hash and exchange order ID

A txid identifies an on-chain transaction. An order or request ID belongs to a service’s internal system. An exchange request can exist before any blockchain transaction is sent, and one service operation may involve more than one on-chain transfer. Supplying the wrong identifier can prevent support staff from locating the relevant stage of an operation.

Approval and transfer

An approval usually gives a smart contract permission to spend up to a specified amount of a token; it does not necessarily move the token immediately. The later contract call may use that allowance. Treat approvals as meaningful authorisations: inspect the spender, amount and application context, and avoid unlimited permissions unless you understand why they are required and accept the risk.

Failed and cancelled

A failed Ethereum transaction was included but its requested state change did not complete; gas used during execution may still be charged. A replacement or cancellation attempt is a separate transaction competing to use the same account nonce. Broadcasting a cancellation attempt does not guarantee that it will replace the original before the original is included.

Practical example: exchanging ETH safely

Suppose you want to exchange ETH for another supported asset. Before creating a request, check the available ETH exchange direction, including the required network and destination details. Availability of a particular pair or network should not be assumed.

1. Identify the asset precisely. Confirm that the source asset is native ETH rather than a token with a similar name or ticker.
2. Match the network. Read the deposit instructions for the specific request. Do not choose a network merely because the destination address looks compatible.
3. Check the destination. Copy the address from the active request, verify it through a trusted display and watch for clipboard-replacement malware.
4. Review the amount and fee. Leave enough ETH to cover gas if the sending wallet deducts the fee from the same balance. Do not infer the current fee from an old transaction.
5. Send a cautious amount when appropriate. A small test transfer can reduce address and network risk, although it creates an additional fee and does not eliminate every risk.
6. Record both references. Keep the exchange request ID and the Ethereum txid because they refer to different parts of the process.
7. Verify on-chain status. Search the txid in a reputable explorer configured for the correct network. Confirm the destination, value and execution status.
8. Wait for the service result. An on-chain success does not necessarily mean the exchange has already completed its internal checks. Verification requirements can vary by operation direction and compliance results, so review the current conditions before creating the request.

ETH is among the assets supported by the service, but this does not imply that every trading pair, blockchain network or transfer route is available. Never send funds based only on a general asset list; use the details generated for the particular operation.

How to recognise the terms in a wallet, explorer or documentation

• In a wallet: Look for the selected network, recipient, asset amount, estimated network fee and a plain-language or decoded description of any contract request. If the wallet cannot explain a contract interaction clearly enough for you to verify it, reject the request and investigate before signing.
• In a blockchain explorer: Search by txid, then compare the transaction status, block information, sender, destination, transferred value and fee. Token movements may appear separately from the transaction’s native ETH value because they are produced by contract execution.
• In token documentation: Find the official contract address and supported network. A ticker alone is not a unique identifier, and search results or unsolicited messages can point to imitation contracts.
• In smart-contract documentation: Separate read operations from write operations. A write request should identify the contract and function being called and will usually require a wallet signature.
• In exchange instructions: Distinguish the service’s request number from the blockchain txid. Check whether an additional identifier is requested, but do not invent a Memo or Tag when the instructions do not provide one.
• In fee information: Look for the estimated total cost rather than reading only a gas-unit figure or a gwei value in isolation. Estimates can change before submission as network demand changes.

Final pre-signing checklist

• The asset is ETH or the exact intended token contract.
• The sending and receiving sides explicitly support the same network.
• The complete destination address has been verified through a trusted source.
• The wallet contains enough ETH for any required Ethereum gas.
• The transaction preview describes the action you intended, not an unexpected approval or contract call.
• No website, message or support representative has requested a seed phrase or private key.
• The fee and amount are acceptable without relying on a promised profit or future price.
• You understand that blockchain transfers are generally irreversible and that a wrong address, wrong network, malicious contract or phishing signature may cause permanent loss.
• You have saved the txid and any separate service request ID for later verification.

Ethereum becomes easier to inspect once each term is tied to a decision: ETH identifies the native asset, the network defines the ledger, the address defines the destination, the signature authorises the action, gas measures the work, the fee pays for execution, and the txid lets you verify the recorded outcome. Check that complete chain before signing rather than trying to correct a transaction after broadcast.