Many currencies have consisted of bank-issued notes which have no inherent physical value, but which may be exchanged for a precious metal, such as gold.
A silver standard was widespread after the fall of the Byzantine Empire, and lasted until 1935, when it was abandoned by China and Hong Kong.
A 20th-century variation was bimetallism, also called the "double standard", under which both gold and silver were legal tender.
Originally fiat money was paper currency or base metal coinage, but in modern economies it mainly exists as data such as bank balances and records of credit or debit card purchases,[3] and the fraction that exists as notes and coins is relatively small.
[6] In times of economic distress, central banks can act as a borrower to prompt the creation of new money as well; during quantitative easing they will buy government bonds and mortgage-backed securities.