Gas Fees in Ethereum Smart contract
In short : “Gas fees is the fee u pay to store data & validate transactions in Ethereum”. e.g.- if user1 send 1.0001eth to user2, user2 got 1eth and 0.0001eth is deducted for transaction/processing, this fee is called Gas fee
Gas fee of Ethereum is not Gas coin (coingecko.com/en/coins/gas).
Gas fee means 0.000000001 Ethereum * processing power.
Standard definition
Gas fees are paid in Ethereum’s native currency, ether (ETH). Gas prices are denoted in gwei, which itself is a denomination of ETH — each gwei is equal to 0.000000001 ETH (10–9 ETH). For example, instead of saying that your gas costs 0.000000001 ether, you can say your gas costs 1 gwei. The word ‘gwei’ itself means person: ‘giga-wei’, and it is equal to 1,000,000,000 wei.
Useful links