What a transaction fee is
A network fee compensates the infrastructure or participants that process and secure transactions. The exact mechanism depends on the blockchain. Some networks use fee markets where users compete for limited block space.
Why fees change
Fees can rise when many users are trying to transact at once. Network design, transaction size, block capacity and fee-market rules all affect the final cost. A fee shown in a wallet is an estimate until the transaction is accepted according to the network’s rules.
Fee is not the same as price
The market price of a coin and the network fee are different concepts. A network may have a low-value token but still require a fee, while a high-value asset can sometimes move with relatively modest network costs.
Before sending
Confirm the network, destination address and displayed fee. Sending an asset on the wrong network can create recovery problems. If a transfer is unfamiliar or unusually large, slow down and verify every detail.