Currency is a monetary unit, which determines money in a particular country. Currency serves the function of the legal tender and regulates payments in the international transactions. All currencies are marked with abbreviations accepted by the International Organization for Standardization. These are three letters, the first two of which mean the country, and the third one is most often the initial of the given currency. For instance the Czech koruna has a symbol CZK, where "CZ" means Czech Republic, and "K" stands for koruna. In today’s world in most of the countries there is one main currency, which is usually divided into 100 smaller units.