Currency is traded in the foreign exchange market. Barter was the preferred method of exchange of goods and services when these were restricted as in ancient times. Exchange of goods was the mode of transaction. The barter system became quite difficult when trade expanded. It became impractical. It became necessary that the trade had to be mediated with something else. That was when coins made of metals that had an inherent value such as gold, silver and copper, were introduced. Coins came to be used for buying and selling goods. It became a convenient mode of transaction. But coins became a problem when the good to be sold or purchased was of high value. Too many coins and too heavy coins posed practical problems. At the same time, trade continued to expand and spread. It was imperative that something had to be done to overcome the problem. Banknotes emerged to substitute coins as it was easy and light to carry around. At the beginning, the banknotes were attached to precious metals as the gold standard. This was however de-linked later. At present the value of the banknotes is what the government decree.