Money is any item or verifiable record that is generally accepted as payment for goods and services and repayment of debts, such as taxes, in a particular country or socio-economic context. The primary functions which distinguish money are as a medium of exchange, a unit of account, a store of value and sometimes, a standard of deferred payment.
Money was historically an emergent market phenomenon that possess intrinsic value as a commodity; nearly all contemporary money systems are based on unbacked fiat money without use value. Its value is consequently derived by social convention, having been declared by a government or regulatory entity 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", in the case of the United States dollar. Contexts which erode public confidence, such as the circulation of counterfeit money or domestic hyperinflation, can cause good money to lose its value.
The money supply of a country comprises all currency in circulation (banknotes and coins currently issued) and, depending on the particular definition used, one or more types of bank money (the balances held in checking accounts, savings accounts, and other types of bank accounts). Bank money, whose value exists on the books of financial institutions and can be converted into physical notes or used for cashless payment, forms by far the largest part of broad money in developed countries.
History
The use of barter-like methods may date back to at least 100,000 years ago, though there is no evidence of a society or economy that relied primarily on barter. Instead, non-monetary societies operated largely along the principles of gift economy and debt. When barter did in fact occur, it was usually between either complete strangers or potential enemies.
Many cultures around the world eventually developed the use of commodity money. The Mesopotamian shekel was a unit of weight, and relied on the mass of something like 160 grains of barley. The first usage of the term came from Mesopotamia circa 3000 BC. Societies in the Americas, Asia, Africa and Australia used shell money—often, the shells of the cowry. According to Herodotus, the Lydians were the first people to introduce the use of gold and silver coins. It is thought by modern scholars that these first stamped coins were minted around 650 to 600 BC.
Medium of exchange
When money is used to intermediate the exchange of goods and services, it is performing a function as a medium of exchange. It thereby avoids the inefficiencies of a barter system, such as the inability to permanently ensure "coincidence of wants". For example, between two parties in a barter system, one party may not have or make the item that the other wants, indicating the non-existence of the coincidence of wants. Having a medium of exchange can alleviate this issue because the former can have the freedom to spend time on other items, instead of being burdened to only serve the needs of the latter. Meanwhile, the latter can use the medium of exchange to seek for a party that can provide them with the item they want.