A gas token is a cryptographic token on the Ethereum blockchain that allows users to optimize transaction costs by storing gas when network fees are low and redeeming it later when fees are higher. Essentially, it functions as a form of prepaid gas, enabling users to lock in lower gas prices during periods of low network activity and utilize these savings when transaction costs spike. This mechanism can significantly reduce transaction fees for frequent Ethereum network users, making it a valuable tool for managing and minimizing transaction costs in decentralized applications (dApps) and transactions on the Ethereum blockchain.