Theta Fuel (TFUEL) is a cryptocurrency used within the Theta network, which is a decentralized video streaming platform. TFUEL is used to incentivize users to share their bandwidth and computing resources to help improve the streaming experience for others on the network. It can also be used for tipping content creators and paying for premium content on the platform. TFUEL can be earned by participating in the network through tasks such as caching and relaying video streams.