Fiat money is not legal tender, but is a popular form of currency for everyday transactions, as there are no physical limitations to its production. It is also the only form of currency that can be used to pay taxes.
Fiat money has been criticized by some economists, who argue that it is inflationary and can lead to financial crises due to overprinting. However, fiat currency is still widely used around the world, and is the dominant form of currency in most countries.