ERC-721

ERC-721 is a token standard that introduced the concept of non-fungible tokens (NFTs) on Ethereum. Unlike ERC-20 tokens, ERC-721 tokens are unique and not interchangeable. This uniqueness makes ERC-721 ideal for creating digital assets with distinct characteristics, such as collectibles, virtual real estate, or artwork. Each ERC-721 token has its own metadata, allowing creators to define its rarity, utility, or ownership. A well-known application of ERC-721 tokens is in the NFT space, where platforms like OpenSea, Rarible, and Decentraland allow users to buy, sell, and trade unique digital assets. The first major use case of ERC-721 tokens was with the game CryptoKitties, where each "kitty" is an NFT with its own attributes, making some kitties more valuable than others. ERC-721 tokens can be used in gaming, digital identity, certification, and various other industries where uniqueness matters.