Gas Limit
The maximum computational work you authorize a transaction to consume — a safety cap on complex operations.
The gas limit is the ceiling on how much computation a transaction may use. A simple transfer needs a small, standard amount (21,000 gas on Ethereum); interacting with a complex smart contract needs more. You set the limit to protect yourself: if a buggy or malicious contract tries to consume runaway computation, the transaction reverts when it hits the limit rather than draining your wallet.
Total fee equals gas used × gas price, so the limit caps your maximum spend. Setting it too low causes an “out of gas” failure (and you still pay for the work done); wallets usually estimate it automatically. Understanding it demystifies failed transactions and the occasional need to raise the limit for gas-heavy DeFi actions.