ERC-721 is a token standard on the Ethereum blockchain that enables the creation of non-fungible tokens (NFTs). Unlike fungible tokens, like Bitcoin or Ethereum, which are interchangeable, each ERC-721 token is unique and cannot be replicated.This uniqueness allows for various applications, such as digital art, collectibles, and virtual real estate. Each token can represent ownership of a distinct item or piece of content, making it valuable in different ways.ERC-721 defines a set of rules and functions that developers can use to create these tokens. This standard includes features for tracking ownership, transferring tokens between users, and ensuring that no two tokens are exactly alike. Due to its flexibility and adoption, ERC-721 has become the foundation for many popular NFT markets and projects. Its widespread use has led to a growing ecosystem where creators, collectors, and investors can interact and engage with unique digital assets.