comptometer

A currency is a component of exchange, facilitating the transfer of supplies and services. It is a form of money, where money is an capable medium of exchange, and it is also considered by a number of people as a store of value, created through a claim to its central bank assets. A currency zone is a country in which a specific currency is the main medium of exchange. To facilitate trade between currency zones, there are exchange price at which currencies can be exchanged beside each other. Currencies can be classified as also floating currencies or fixed currencies based on their exchange rate regime.

In general usage, currency at times refers to only paper money, as in "coins and currency", but this is confusing. Coins and paper money are both forms of currency.
In most cases, each country has control over the supply and manufacture of its own currency.