ERC-721 is the token standard within the Ethereum blockchain representing non-fungible tokens (NFTs). An ERC-721 token can be assigned different values than other tokens which emerge from the same smart contract based on other defining characteristics. ERC-721 tokens can represent real-world assets on the blockchain, allowing users to tokenize any goods or services with physical value.
ERC-721 stands for Ethereum Requests for Comments 721. It was initially proposed in January 2018 by William Entriken, Dieter Shirley, Jacob Evans, and Nastassia Sachs. They are different from ERC-20 tokens as they are non-fungible, meaning each token is unique and cannot be interchanged with another ERC-721 token.