Gas or other forms of transaction fees are costs that users pay to execute transactions on blockchains. Gas fees are paid to network validators and miners who secure, verify, and process transactions. These fees incentivize validators to participate in the network while helping prevent network overloads and manipulation from spam transactions. Transaction fees vary by network congestion, similar to supply and demand dynamics.
https://www.kraken.com/learn/what-is-a-blockchain-gas-fee
https://help.1inch.io/en/articles/4585052-what-is-gas-and-why-do-i-need-native-assets-to-pay-for-transaction-fees
https://www.coinbase.com/learn/crypto-basics/what-are-gas-fees