Ethereum is a blockchain network that allows for the creation and execution of smart contracts. In order to use the network and execute these smart contracts, a small fee must be paid in the form of "gas." This fee is measured in "gwei," which is a denomination of the cryptocurrency Ether (ETH).

The gas fee is essentially a way to pay for the computational power required to execute the smart contract. The more complex the contract, the more gas it will require and the higher the fee will be. Gwei is the unit used to measure the amount of gas fee.

You can think of Gwei as the "cents" of Ethereum and Gas fees as the "dollar" cost for executing smart contract on Ethereum blockchain.

Priority fee is the recommended gas price for transactions to be processed within a reasonable time frame, usually under 10 minutes. Setting a higher priority fee means the transaction will be processed faster, but at a higher gas cost (in ETH). Setting a lower priority fee may result in slower processing or even failing to be processed if the network is congested.

To learn about the technical details behind gas fees and gwei, click here.