Forex pairs are always involved in currency trading. The pair is the two currencies involved in your trade. For example if you are exchanging US dollars for Swiss francs, the currency pair is USD/CHF.

Theoretically you could trade any two currencies of the world, but in practice most foreign exchange trading is limited to the currencies of the larger financial powers. This does not necessarily mean the biggest or most politically powerful countries. Switzerland for example is only a small country but is a major player in the financial markets because of the global importance of the Swiss banks.

There are 6 major forex pairs which between them account for 90% of the funds traded on the forex markets. These are: