Currency trading is the main activity of the foreign exchange market. The barter system was the prevalent system in the ancient days when trade was limited in volume and in geography. In this system, goods were exchanged directly. As trade expanded, the barter system became unwieldy. Something had to be done to make transaction manageable. That was when coins were introduced as a convenient intermediary for exchange of goods. The coins were made from precious metals as gold, silver as well as copper. It became convenient now to buy and sell goods. However, there was a catch. When the goods were of higher value, coins became problem. More coins and heavier coins caused a problem. With trade expanding even more, it became all the more important that a solution had to be found. That was when banknotes came to be introduced to add to the coins as representing higher value. The banknotes, in order to have a value, were pegged to valuable metals as the gold standard. However, later this was de-linked and now its value is as decreed by governments. The central banks controlled by national governments issued these banknotes.