Ethereum is a blockchain that can run smart contracts: programs executed by its network. Applications can use these programs to manage tokens and other shared rules.
Ether, usually written ETH, is the network’s native cryptocurrency. Ethereum names the network; ether names the asset. ETH pays transaction fees, including the cost of computation commonly described as gas.
How transactions are secured
Ethereum moved to proof of stake in 2022. Validators stake ETH to participate in proposing and checking blocks. This differs from Bitcoin’s proof-of-work mining. Using the same word “cryptocurrency” for both does not mean their networks operate in the same way.
Ethereum is the network; ETH is the asset
Ethereum provides the shared computing environment, while ether pays for transactions and helps secure the network. Keeping those terms separate makes fees, staking, and application activity easier to understand.
Gas and transaction costs
Gas measures the computational work of an Ethereum transaction. A simple transfer and a complex smart-contract interaction can consume different amounts. The fee also depends on network conditions, so a previous transaction’s cost is not a fixed price for the next one.
Wallets normally show an estimate before submission. Gas pays for network computation; it is separate from any service fee charged by an exchange or application.
Computation creates a transaction cost
Every operation performed by the network consumes gas. A simple ETH transfer normally needs less computation than a complex smart-contract interaction, so the two can have very different fees.
Sources
Educational information, not investment advice.