All terms
The fee you pay to have the network process your transaction.
Gas is the unit measuring computational work on Ethereum and similar chains. A simple transfer costs 21000 gas. A complex swap might cost 200000. You pay gas units multiplied by a gas price, denominated in the network's native token.
Gas exists to stop spam. If computation were free, anyone could paralyze the network with junk. Attaching a real cost makes attacks expensive and prioritizes transactions people actually care about.
On Ethereum a swap might cost several dollars. The same swap on Base or Solana costs a fraction of a cent, which is the entire reason layer 2 networks exist.
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