Currency and exchange were important elements of trade in the ancient world, enabling people to buy and sell items like food, pottery, and raw materials.[9] If a Greek coin held more gold than an Egyptian coin due to its size or content, then a merchant could barter fewer Greek gold coins for more Egyptian ones, or for more material goods. This is why, at some point in their history, most world currencies in circulation today had a value fixed to a specific quantity of a recognized standard like silver and gold.

Currency carry trade refers to the act of borrowing one currency that has a low interest rate in order to purchase another with a higher interest rate. A large difference in rates can be highly profitable for the trader, especially if high leverage is used. However, with all levered investments this is a double edged sword, and large exchange rate price fluctuations can suddenly swing trades into huge losses.

^ The total sum is 200% because each currency trade always involves a currency pair; one currency is sold (e.g. US$) and another bought (€). Therefore each trade is counted twice, once under the sold currency ($) and once under the bought currency (€). The percentages above are the percent of trades involving that currency regardless of whether it is bought or sold, e.g. the U.S. Dollar is bought or sold in 88% of all trades, whereas the Euro is bought or sold 32% of the time.
Forex brokers provide leverage up to 50:1 (more in some countries). For this example, assume the trader is using 30:1 leverage, as usually that is more than enough leverage for forex day traders. Since the trader has $5,000, and leverage is 30:1, the trader is able to take positions worth up to $150,000. Risk is still based on the original $5,000; this keeps the risk limited to a small portion of the deposited capital.
Forex is a portmanteau of foreign currency and exchange. Foreign exchange is the process of changing one currency into another currency for a variety of reasons, usually for commerce, trading, or tourism. According to a recent triennial report from the Bank for International Settlements (a global bank for national central banks), the average was more than $5.1 trillion in daily forex trading volume.