fiat currency

 Fiat currency by definition is government-issued currency that is not backed by a commodity such as gold.  The US dollar has not been on the gold standard since 1971.  Most of the US dollars don't actually exist in physical form and are in fact digital dollars.  Fiat money comes into existence when debt is created, when loans are made new fiat money is generated.  Anytime a government backed entity / central bank backed entity is able to issue credit, new money is made.  Getting others into debt by loaning money out of thin air then collecting on the interest is like how gold prospection to gold.