The term gas limit refers to the maximum price a cryptocurrency user is willing to pay when sending a transaction, or performing a smart contract function, in the Ethereum blockchain. These fees are calculated in gas unit, and the gas limit defines the maximum value that the transaction or function can “charge” or take from the user. As such, the gas limit works as a security mechanism that prevents high fees from being incorrectly charged due to a bug or error in a smart contract.
Some wallets and service provide setup the gas prices and gas limit automatically, but in some cases, users are also able to adjust them manually, according to their needs. In general, a regular Ether (ETH) transaction would be made with, at least, a 21,000 gas limit. If the gas limit and gas price (Gwei) are set to a higher level, the operation will occur much faster. Still, faster operations will likely charge higher fees. On the other hand, a very low gas limit and gas price would be risky because transactions could take too long to be confirmed, or even get stuck (fail).
However, what really defines the value paid for transaction fees is the gas price. The gas price is more influential than the gas limit because the latter is just a definition of the maximum value. In other words, the total cost of a transaction is the gas price (in Gwei) multiplied by the gas limit, which will result in the amount of Ether to be paid.