As mentioned in the introduction, a token contract can take any form, as long as there is a way to map between an address and a token balance. However, standard token implementations are available that contract creators can use. These standard implementations provide a simple and uniform interface through which interactions with contracts can occur, and allow wallets and exchanges to easily list a multitude of tokens while only implementing the integration logic once.

These standards are defined as Ethereum Request for Comments (ERC) token standards, and are submitted through the Ethereum Improvement Proposal (EIP) process. The open source nature of Ethereum means that anybody can submit such a proposal to the community for discussion and consideration.

Various token standards exist, the most important of which we'll discuss here. It's important to note that the standards define an interface, which defines what a token contract can do, but not how it does it. The implementations are not defined by the standards.