By currency we generally mean coins and paper notes that are issued by a government and circulated within an economy. In a broader sense, it is a medium of exchange for goods and services.
Most countries issue banknotes and coins, generally known as fiat money, which are regulated by central banks.
Modern advancements in technology have given birth to a new form of currency -- digital currency or cryptocurrency -- which is an internet-based medium of exchange allowing instantaneous transactions. Digital currencies, such as bitcoin, are also decentralised. While supporters think digital currencies are superior to other forms, critics say they are weird.
However, there are still people who resort to ancient forms of exchange such as livestock and commodities.
Necessity has forced some people to use strange "currencies". Due to massive coin shortages in Argentina, shops have had to resort to using candy for change. There was also a girl in Brazil who recently sold 5'2" of her hair for $5,000 to help pay for her family's home.
Emerging Verticals has compiled a list of the world's weird currencies and produced an interactive map showing their details.
The list includes shells, bitcoin, pigs, Shiitake Mushrooms, rai stones, goats, bottle caps, salt, peppercorns salmon and cacao.