Definition: Gas is a unit that measures the computational effort (like processing and storage) required to execute a transaction on Ethereum.
Key Rules:
Gas Limit : The maximum amount of "fuel" you are willing to pay for a transaction. If it's too low, the transaction fails mid-way; however, the fee is still charged because miners have already performed the work.
Refunds : If the actual Gas consumed is less than your set limit, the excess is automatically credited back to your wallet.
Miner Incentives : The higher the price you are willing to pay per unit of Gas (Gas Price), the more likely miners are to prioritize and process your transaction quickly.