Transactions that are EIP1559-compliant have two portions: a Miner Tip and a Base Fee. Miner Tips represent the portion of the total transaction fees that rewards miners. This serves as an optinal incentive mechanism for miners to prioritize transactions that have opted-in and paid a tip. Base Fees, on the other hand, are mandatory and represent the minimum amount needed to be paid for a transaction to be included in a block. After inclusion, the Base Fee is effectively taken out of circulation, and it is burnt (destroyed).