Major
Since the Bretton Woods Agreement of 1944, the United States has been the global reserve currency, which makes the US dollar (USD) the currency of choice in international trade. It’s the most important of the majors.
The euro (EUR) is the second most traded currency, followed by the Japanese yen (JPY), the pound sterling (GBP), the Australian dollar (AUD), the Canadian dollar (CAD), and the Swiss franc (CHF).
A major currency pair is the US dollar paired against any of the above currencies.
Minor
The minor, or cross, currencies comprise all of the above major currencies when paired against each other without the US dollar.
Exotic
The exotic currency pairs are those that feature the currency of an emerging market or less liquid currency in terms of global turnover on one side of the pair.