Priority fee
Also: tip, priority tip
A priority fee is a payment on top of the base network fee that improves the odds of your transaction being included in a block quickly. On Solana it is priced per compute unit, and wallets and swap apps usually set it automatically or let you pick a level. On EVM networks such as Ethereum or Base, the priority fee is a tip to the block producer added to the base fee.
During hot memecoin launches many people and bots compete for space in the same blocks, so priority fees climb. One that is too low can leave a transaction delayed or expired. One that is too high is money thrown away, especially on small buys where the fee can exceed the swap itself.