A token is a representation of something in blockchain. This something can be money, services, shares in a company or anything. By representing something as tokens, we can allow smart contract to interact with them.
IRC2 token is a standard token equivalent to ERC20 for ICON blockchain. It helps to keep track of fungible tokens.
There are a few core contracts to implement IRC2 token.
IIRC2: Interface IRC2 methods should confirm into.