Unlike stocks or commodities, foreign exchange transactions do not take place on an exchange; in fact, currencies are traded directly between two parties in what is called the over-the-counter (OTC) market. This means that the foreign exchange market operates through a global network of banks, distributed in four major trading centers in different locations: London, New York, Sydney and Tokyo. In addition, since there is no single center through which all operations must pass, it is possible to operate 24 hours a day.