Gwei is a unit of measurement for the cost of gas on the Ethereum blockchain. Gas is a term used on the Ethereum network to refer to the fee that is paid for processing transactions and executing smart contracts.

Gas fees are measured in "wei", which is the smallest unit of Ether (ETH), the native cryptocurrency of the Ethereum network. One GWEI is equal to 1 billion wei, and is often used as a more convenient and intuitive unit of measurement for gas fees.

The cost of gas, and therefore the cost of GWEI, can vary depending on a number of factors, such as the current network congestion, the complexity of the transaction or smart contract, and the amount of ETH being sent. GWEI is often used by Ethereum users and developers to estimate and compare the cost of different transactions and actions on the Ethereum network.