fee
Transaction fees are small amounts of bitcoin paid to miners for including a transaction in a block. They are measured in sat/vbyte and rise when network demand is high.
A transaction fee is a small amount of bitcoin included in every transaction and paid to the miner who includes that transaction in a block. Fees serve two purposes: they compensate miners for the computational work and storage space required to process transactions, and they create a cost barrier that discourages spam transactions from clogging the network.
Transaction fees on Bitcoin are calculated based on the size of the transaction in virtual bytes (vbytes), not the value being sent. The fee rate is expressed in satoshis per virtual byte (sat/vbyte). A transaction with many inputs and outputs takes up more space and therefore requires a higher absolute fee to be competitive. When block space is in high demand, users compete by offering higher fee rates to get their transactions confirmed quickly.
The miner who successfully mines a block collects all the transaction fees from the transactions included in that block, in addition to the block reward. As the block reward decreases through successive halvings, transaction fees are expected to make up a growing share of the total income for miners, sustaining the economic incentive to secure the network over the long term.