Currencies are traded against one another in pairs. Each currency pair thus constitutes an individual trading product and is traditionally noted XXXYYY or XXX/YYY, where XXX and YYY are the ISO 4217 international three-letter code of the currencies involved. The first currency (XXX) is the base currency that is quoted relative to the second currency (YYY), called the counter currency (or quote currency). For instance, the quotation EURUSD (EUR/USD) 1.5465 is the price of the Euro expressed in US dollars, meaning 1 euro = 1.5465 dollars. The market convention is to quote most exchange rates against the USD with the US dollar as the base currency (e.g. USDJPY, USDCAD, USDCHF). The exceptions are the British pound (GBP), Australian dollar (AUD), the New Zealand dollar (NZD) and the euro (EUR) where the USD is the counter currency (e.g. GBPUSD, AUDUSD, NZDUSD, EURUSD).
Second, since trades don't take place on a traditional exchange, you won't find the same fees or commissions that you would on another market. Next, there's no cut-off as to when you can and cannot trade. Because the market is open 24 hours a day, you can trade at any time of day. Finally, because it's such a liquid market, you can get in and out whenever you want and you can buy as much currency as you can afford.
Traders at the banks would collaborate in online chat rooms. One trader would agree to build a huge position in a currency, then unload it at 4 p.m. London Time each day. That's when the WM/Reuters fix price is set. That price is based on all the trades taking place in one minute. By selling a currency during that minute, the trader could lower the fix price. That's the price used to calculate benchmarks in mutual funds. Traders at the other banks would also profit because they knew what the fix price would be.
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.