Most NFTs are created using the Ethereum blockchain through the ERC-721 Non-Fungible Token Standard. ERC 721 is a standard which outlines how an NFT should be created so that it will be properly recognized across the Ethereum ecosystem. When an ERC-721 NFT is created, a file of metadata โ literally data which provides information about other data (hence, โmetaโ) โ provides information about the NFT. The easiest way to think of it is that the NFT itself is a contract that proves ownership of another item, which is detailed in that metadata. In the case of the most common NFTs, which are digital art, the actual JPG or file of the art is usually stored off the Ethereum blockchain and the metadata includes a link to that file. This means that the actual file or artwork can be altered since it is not embedded in the blockchain.
