the foreign exchange market, or forex market, is the most liquid market in the world. In this market, government, banks and some multinational companies trade currencies from several countries.
The process always involves two currencies: buying one currency while selling another. The opportunities of profit is then in all cases, whether the currency goes up or down. Let’s take an example: USD/EUR this is what we call a pair. The US dollar/Euro is the most volatile pair and then the most profitable one.
Suppose you are expecting a good US economy’s condition, then the US Dollar will increase, that is why you will go long in this pair, which means you will buy US dollar while selling EUR. When the USD goes up then you will go short, meaning that you will sell the Dollars that you already bought.
On the other had, if you expect a weak dollar, you may too profit from it. In this case, you will go short with this pair: selling USD and in the same time you are buying EUR. When the USD goes down it means the EUR is up, then you will sell the EUR you have.
The advantages of the forex market is that it is very liquid: any time you can buy or sell instantly. This market is also hard to manipulate because of the important amount of currencies traded. No country can manipulate the market for its profit.