Transaction Fees / Gas Fees
A transaction fee is the payment to miners or validators for including your transaction in a block; on Ethereum it is called gas.
In depth
Block space is limited, so fees act as an auction — pay more and you are confirmed sooner. Bitcoin fees scale with the transaction’s size in bytes; Ethereum gas scales with the computation your transaction demands. Fees rise sharply during congestion and fall when the network is quiet.
Why it matters
Network fees are separate from exchange fees — they explain why a withdrawal costs a small, variable amount.