EIP-1559 introduces a new Ethereum transaction fee mechanism. The transaction fee of this new model consists two elements: a base fee which is burned, and a tip which is allocated to miners. The base fee depends on the allocation of scarce block space to users, while the tip depends on other fee market factors.
For users: Base fee is a must and is determined by the usage of scarce block space. Priority fee to be paid to miners is settable. In most cases, the higher the priority fee, the faster the speed of transactions being confirmed on Ethereum blockchain.
When setting the gas fee of an Ethereum transaction, you can tap on "Custom" and then tap on the on-off button on the right of EIP-1559 to set "Gas Limit", "Max Priority Fee" and "Max Fee".
Gas Limit is the amount. Max Priority Fee and Max Fee are the prices, of which the unit is GWEI. 1ETH=10^9 GWEI
The product of "Gas Limit" and "Max Priority Fee" is the maximum gas fee of this transaction for miners. The product of "Gas Limit" and "Max Fee" is the maximum total gas fee of this transaction.
If the gas limit is set too low, the transaction might fail.
If the gas price is set too low, it might take a very long time for the transaction to be confirmed. When the transaction is not confirmed yet, you can't create a new transaction sending to a different address. If you don't want to keep waiting, you can create a new transaction sending to the same address to replace the former transaction.