At its core, a token is a kind of debt, receipt or contract with a promise to the owner to provide a certain product or service. For example, a subway token or transport ticket is a token that entitles you to travel.Cryptocurrency is an internal unit of account of any public blockchain that uses mining (in the form of P-o-W or P-o-S). Mining is a necessary and important process in the public blockchain and cryptocurrency acts as an incentive for miners. Additionally, cryptocurrency is used for transaction fees. It can also be sold (exchanged for Fiat money).