The big currencies in most peoples estimation are the US dollar (USD), Euro (EUR), yen (JPY), pound (GBP), Swiss frank (CHF), and the Canadian and Australian dollars (CAD and AUD). Therefore, there are six major pairs where USD is mixed with any other of the majors. Cross pairs are those not including USD, such as CBP/CHF.
These are the best forex pairs for a retail trader to work on. Sometimes, if a broker offers any minor currencies for trading, the spread will be high. The exception might be that a broker will offer the currency of their own country at competitive rates regardless of if that currency is not a major.
So you can trade any major pair or cross of the majors but unless you have reasons for doing otherwise, most amateurs are recommended to begin with EUR/USD for many trading. First, there is a lot of competition between brokers so the spread is generally lowest for this pair. 2nd, the high liquidity implies that there will probably be less slippage, and you are more likely to get the price that you see on screen.
If you are using an expert counsellor or foreign exchange trading robot, on the other hand, it could be set up for other pairs. If that is so it is best to use it according to its settings. That will not work so well on any but the suggested pairs, so those will be the best currency exchange pairs for an expert advisor.
