In contrast to the world's stock markets, foreign exchange is traded without the constraints of a central physical exchange. Transactions are instead conducted via telephone or online. With this transaction structure as its foundation, the Foreign Exchange Market has become by far the largest marketplace in the world.
Buying and Selling
In the forex market, currencies are always priced and traded in pairs. You simultaneously buy one currency and sell another, but you can determine which pair of currencies you wish to trade. For example, if you believe the value of the euro is going to increase vis-á-vis the U.S. Dollar, then you would go long on EUR/USD instrument (currency pair). Obviously, the objective of forex currency trading is to exchange one currency for another in the expectation that the market rate or price will change so that the currency you bought has increased its value relative to the one you sold. If you have bought a currency and the price appreciates in value, then you must sell the currency back in order to lock in the profit. An open trade or position is one in which a trader has either bought / sold one currency pair and has not sold / bought back the equivalent amount to effectively close the position.