Money is anything that is generally accepted as payment for goods and services and repayment of debts. The main functions of money are distinguished as: a medium of exchange, a unit of account, a store of value, and occasionally, a standard of deferred payment.

Money originated as commodity money, but nearly all contemporary money systems are based on fiat money. Fiat money is without value as a physical commodity, and derives its value by being declared by a government to be legal tender; that is, it must be accepted as a form of payment within the boundaries of the country, for "all debts, public and private".

The money supply of a country consists of currency (banknotes and coins) and demand deposits or 'bank money' (the balance held in checking accounts and savings accounts). These demand deposits usually account for a much larger part of the money supply than currency. Bank money is intangible and exists only in the form of various bank records. Despite being intangible, bank money still performs the basic functions of money, being generally accepted as a form of payment.