FIAT money is a legal tender like the US ($) dollar or Euro (€) that is tied to a government-issued currency. FIAT can be used as physical notes or electronic payments using online banking and debit or credit cards. FIAT currency is backed by a central government and its supply is also controlled by the government.
Cryptocurrency is a purely digital asset that is created on and derives value from its native blockchain. Cryptocurrency is a decentralised asset governed by cryptography and its supply is controlled by an algorithm. Common examples are Litecoin (LTC), Bitcoin (BTC), Ether (ETH).