Gas fee

What you pay the network to process a transaction. It changes with demand.

A gas fee is paid to the network, not to your wallet provider, to include your transaction in a block. On Ethereum and similar networks it's paid in the network's own coin, such as ETH.

Fees rise when the network is busy. You need a little of the network's coin in your wallet to pay them, even when sending a different token. Revoking a token approval also costs a gas fee.