Currencies are traded on the Foreign Exchange market, also known as Forex. This is a decentralized market that spans the globe and is considered the largest by trading volume and the most liquid worldwide. Exchange rates fluctuate continuously due to the ever changing market forces of supply and demand. Forex traders buy a currency pair if they think the exchange rate will rise and sell it if they think the opposite will happen. The Forex market remains open around the world for 24 hours a day with the exception of weekends.
In 1944, the Bretton Woods Accord was signed, allowing currencies to fluctuate within a range of ±1% from the currency's par exchange rate. In Japan, the Foreign Exchange Bank Law was introduced in 1954. As a result, the Bank of Tokyo became a center of foreign exchange by September 1954. Between 1954 and 1959, Japanese law was changed to allow foreign exchange dealings in many more Western currencies.
Unlike stock markets, which can trace their roots back centuries, the forex market as we understand it today is a truly new market. Of course, in its most basic sense—that of people converting one currency to another for financial advantage—forex has been around since nations began minting currencies. But the modern forex markets are a modern invention. After the accord at Bretton Woods in 1971, more major currencies were allowed to float freely against one another. The values of individual currencies vary, which has given rise to the need for foreign exchange services and trading.