Because they are non-fungible, ERC-721 tokens are different from ERC-20 tokens. As a result, each token is distinct and cannot be used with another token. Taking apart ERC Ethereum Request for Comments is referred to as ERC. This isn't a technology or platform; rather, it offers technical advice to builders. There are nine final Ethereum Requests for Comments as of December 2018. ERC-20, ERC-55, ERC-137, ERC-162, ERC-165, ERC-181, ERC-190, and ERC-1167 are some examples of ERCs. By submitting an Ethereum Improvement Proposal (EIP), developers can construct an ERC. Due to limitations in the ERC-20 interface, William Entriken, Dieter Shirley, Jacob Evans, and Nastassia Sachs developed ERC-721 - The Non-Fungible Token Standard. by way of an Ethereum Improvement Proposal (EIP) made on January 24th, 2018. ERC-721 was used by the well-known Ethereum decentralized application Cryptokitties to produce one-of-a-kind digital collectibles in the shape of cats. According to the marketplace's users, every kitten had a different value for each buyer. Every kitten is different and fetches a different price, therefore each token must be special. Physical property (including buildings, works of art, and automobiles) is made possible by the development of non-fungible tokens based on the blockchain. Cryptokitties, rare Pepes, collectible cards, and other virtual collectibles loans are assets with a negative value. The contract must adhere to both the ERC-721 and ERC-165 interfaces in order to create an ERC-721 token.