Forex trading, also known as Foreign Exchange Trading or FX Trading, is a relatively recent phenomenon. In fact, until the collapse of the 1944 Breton Woods Agreement (initiated to keep cash from draining out of war-ravaged Europe) it wouldn't have been possible at all. Today the foreign exchange market is the largest, most liquid and most influential market in the world. It is a truly 24 hour global market trading in excess of $1.5 trillion dollars a day, making it far bigger than the combined total of all the world's stock exchanges.
Participants in Forex trading include central banks, corporations, individual investors, speculators, and hedge funds. With the advent of electronic trading platforms, smaller investors and financial firms now have access to the same liquidity as larger operators. Trading on margin (meaning you can trade more capital than you actually have) is possible as the volatility of currency pairs is usually less than other markets, such as futures and equities. If you were to trade £100,000 Sterling - US Dollars you would only need £1000 in your account at 1% margin to open the trade. Trading on margin is a double edged sword though as you can lose money as fast as you make it.
Trading, or speculation, makes up 95% of the daily volume of the international FX market while the remaining 5% is accounted for by governments and commercial companies converting one currency into another in the course buying and selling goods and services.
Liquidity, or the ability of an asset to be bought or sold without a significant movement in value, is the major appeal of Forex trading. The Forex market is the most liquid market in the world and most speculators focus on trading the highly liquid majors (the US Dollar, Japanese Yen, Euro, British Pound Sterling, Canadian and Australian Dollars) where approximately 85% of trading volume occurs.
The trade is always done in pairs, where one currency is bought and the other sold, with the first currency referred to as the "base currency" expressed as one monetary unit of exchange and the second, the "counter or quote currency". The dominant base currencies are the Euro, the Pound and the US Dollar although it may not be too long before the Chinese Yuan or RMB joins that list.
For example, you may buy British pounds (base currency) against Euros, anticipating the Pound to increase in value relative to the Euro. If the Pound does rise relative to the Euro, you sell your position and you have made a profit.
The high liquidity in Forex means that trades will generally be filled at the order price and there are always plenty of buyers and sellers which helps to make sure spreads are narrow. Forex trading is extremely demanding though since the market is "always open" and traders often need to be highly reactive, responding to economic and political events that may force their hands earlier or later than they may have planned.
