Currency
Traditionally you may not think about the idea of currency from your day to day life. If you live in the United States then you are probably familiar with the US Dollar or USD. This is an example of Fiat Money. Lets next take a dive in on that.
Fiat Money
Fiat money is not backed by any commodity. Let me give you an example, The US government used to back all of its currency with Gold.
Representative Money
The usual alternative to Fiat Money is Commodity-backed or Representative Money. In this system you issue tokens or notes which represent the underlying backed commodity.
Commodity Money
Another way of having commercy with a currency is Commodity Money, where the issued note is actually of value. Gold coins would be a good example of this.