Fiat money (from Latin: fiat, "let it be done") is a type of currency that is not backed by any commodity such as gold or silver. It is typically designated by the issuing government to be legal tender. Throughout history, fiat money was sometimes issued by local banks and other institutions. In modern times, fiat money is generally authorized by government regulation.

Fiat money generally does not have intrinsic value and does not have use value. It has value only because the individuals who use it as a unit of account – or, in the case of currency, a medium of exchange – agree on its value.[1] They trust that it will be accepted by merchants and other people.

https://en.wikipedia.org/wiki/Fiat_money

Fiat currencies are government-issued currencies that have the backing of the sovereign; cryptocurrencies, on the other hand, are decentralized digital coins or assets that are held together through the blockchain technology.

https://www.outlookindia.com/business/crypto-vs-fiat-what-s-...