Gas fees are charges users have to pay whenever they perform a transaction on a blockchain network, such as Ethereum. These fees are charged as compensation for the computing energy consumed for processing and validating transactions on the blockchain network.
It can be likened to the fuel that keeps the Ethereum network up and running and is the fee needed for performing a successful transaction on the blockchain. Users pay gas fees in ETH - Ethereum's native cryptocurrency.
In Ethereum, gas fees are denoted in Gwei, with a value of 0.0000000001 ETH. The process of calculating gas fees on the Ethereum network changed in August 2021 following the rollout of the London Upgrade.