When something is fungible, in this case a token, it means it can be easily replaced by something identical — and it is easily tradable. Numerous tokens and undoubtedly cryptocurrencies are fungible. In the event that you send somebody a Bitcoin, and get one back, you wouldn’t see any difference. Most of the time, fungible tokens are built using a standard called ERC-20. For the sake of simplicity, let’s imagine each of these tokens is a $1 bill. If you sent a token to someone, and got another one back a week later, they would be identical.