ERC-721 is a token standard used on the Ethereum blockchain that defines a set of rules for creating non-fungible tokens (NFTs). Unlike fungible tokens, which are identical and can be exchanged on a one-to-one basis, each ERC-721 token is unique and has distinct properties. This uniqueness allows them to represent individual assets, such as art, collectibles, or virtual real estate.The standard outlines how these tokens should be structured, including how they can be created, transferred, and interacted with by users and applications. Features like ownership tracking and the ability to mint new tokens are essential to its functionality.Due to its unique characteristics, ERC-721 has gained popularity for projects that require verified ownership of specific digital items. It allows creators and collectors to prove authenticity and scarcity, enhancing the value and marketability of their assets. Overall, ERC-721 has played a significant role in popularizing NFTs and has enabled a wide variety of innovative applications.