Numismatics is the study or collection of currency, including coins, tokens, paper money, and related objects. While numismatists are often characterized as students or collectors of coins, the discipline also includes the broader study of money and other payment media used to resolve debts and the exchange of goods.
Source: http://en.wikipedia.org/wiki/Numismatics
I collect worldwide coins, paper money and related objects (such as: phone cards, tokens).