EIP-3009

In plainer words

Imagine you have a check, but you don't want to go to the bank yourself (pay the fee). EIP-3009 lets you sign the check offline, then a friend takes it to the bank and pays the gas. That's 'off-chain signature, someone else pays gas.' In USDC transfers, you don't need to send a transaction. You just sign a proof saying 'allow this amount to be moved.' Anyone can submit that proof to the blockchain, and they pay the gas fee. So you can transfer money for free, but the other party might charge a service fee. This standard is the foundation for x402 gasless payments. x402 lets AI agents or websites request a user's signature, then the service provider pays the gas, making the payment invisible to the user. Like clicking 'agree' online, money is deducted, but you don't pay transaction fees. Note that signatures have expiry and limits to prevent abuse. But details are still evolving, and implementations may vary.