For example – the rate you find for GBP/USD represents the number of US dollars one British pound will buy you. So, if you have reason to believe the pound will increase in value versus the US dollar, you’d look to purchase pounds with US dollars. However, if the exchange rate climbs, you’d sell your pounds back and make a profit. Likewise with Euros, Yen etc
Forex is a portmanteau of foreign currency and exchange. Foreign exchange is the process of changing one currency into another currency for a variety of reasons, usually for commerce, trading, or tourism. According to a recent triennial report from the Bank for International Settlements (a global bank for national central banks), the average was more than $5.1 trillion in daily forex trading volume.