It is common knowledge that there are tokens of different standards: ERC-20, ERC-223, ERC-721 and others. Some are used in the Ethereum blockchain ecosystem, others in video games. The ERC-721 token was, let’s say, an unnecessary link: it is not interchangeable, unlike the ERC-20 on which many crypto projects are built. Each such token has a price that varies from the value of what the token represents. It was originally created for Cryptokitties: there are kittens in the game (which are implemented with these tokens). They differ in breed, color, size, and cost.