What Are ERC721 Tokens?
ERC721 tokens, more commonly referred to as Non-Fungible tokens (NFTs) have captured a lot of developer mindshare since the interface was first published as an EIP in September of 2017. Non-Fungible tokens allow developers to tokenize ownership of any arbitrary data, drastically increasing the design space of what can be represented as a token on the Ethereum blockchain.
The biggest differentiator of Non-Fungible tokens is that each one is tied to a different identifier, making each token unique to its owner. This is much different to tokens leveraging the ERC20 token standard, which is a token standard for fungible tokens, meaning each token is interchangeable. In the ERC20 token standard, developers can create any number of tokens within one contract, but in the ERC721 token standard, each token within the contract holds a different value.
ERC721 is a standard interface for Non-Fungible tokens, meaning ERC721 tokens are simply a subset of Ethereum tokens.