A currency is a fiat currency that is to say that it consists of coins and bank notes. It is issued by the central bank of each country and its value depends on the trust we give him.
On the forex, currencies are quoted in pairs, we speak of the level of a currency compared to another currency and this level corresponds to what is called the exchange rate.
Currencies of the forex market are designated by an abbreviation of 3 letters. The first two correspond to the country of origin, in English, and the third in the name of the currency. Specifically, the u.s. dollar is called the USD on the forex, and this means United States Dollar, the pound sterling is called, GBP for Great Britain Pound. The euro is an exception, for its acronym EUR is simply an abbreviation of the name euro.
We trade on forex the currencies of virtually all countries. Here is a short list of the major currencies trade : canadian dollar (CAD), australian dollar (AUD) and new zealand (NZD), Polish zloty (PLN), japanese yen (JPY), israeli shekel (ILS), brazilian real (BRL), the south african rand (ZAR), etc.
Some currencies have more value than others on the market, they are called the major currencies. These last are present in most transactions. It is located in the top of the list the u.s. dollar, then the euro, the japanese yen, the british pound, and a little further on the canadian dollar, australian and new zealand as well as the swiss franc.
Generally, it is advisable to start trading foreign currencies the most popular of the market because it is much easier to determine the direction they will take. You will find, in fact, on the internet many resources to perform analysis technical and fundamental.