What gas fees pay for
Every transaction uses network resources to be validated and recorded. The gas fee compensates validators for that work. More complex actions, like swaps or contract interactions, use more resources and therefore cost more than a simple transfer.
Why fees rise and fall
Fees are driven by demand. When many people transact at once, the network gets congested and fees climb. During quiet periods, fees drop. This is why the same swap can cost very different amounts depending on the time of day.
Native coins pay the fee
Fees are paid in the network's native coin, such as ETH on Ethereum or SOL on Solana. You need a small balance of that coin to move tokens on the same network. If you have tokens but no native coin, a transaction can fail for insufficient gas.
Reducing what you pay
You can lower costs by transacting when the network is less busy, batching actions when possible, and reviewing the estimated fee before you confirm. Always keep a little native coin available so transfers do not fail unexpectedly.