Explanation:

Fiat money is a currency established as money by government regulation or law. The term derives from the Latin fiat ("let it become", "it will become")[2] used in the sense of an order or decree. It differs from commodity money and representative money. Commodity money is created from a good, often a precious metal such as gold or silver, which has uses other than as a medium of exchange (such a good is called a commodity), while representative money simply represents a claim on such a good.
Legal tenders are the coins or banknotes that must be accepted if offered in payment of a debt.
Flat money is a legal tender for settling debts. it is a paper money that is not convertible and is declared by government to be legal tender for the settlement of all debts..