Each blockchain has its own way to represent a fungible token:
A) By providing a common interface or standard, like Ethereum with the well-known ERC-20.
B) or by incorporated into the blockchain a fungible token implementation.
Fungibility describes a commodity, security, or other good that is mostly interchangeable with other units of the same kind. For example, as a real-world analogy, a 10 USD bill can be interchanged with another 10 USD bill. They have the same value.