The Foreign Exchange market, also called FOREX or FX, is the global market for currency trading. With a daily volume of more than $5.3 trillion, it is the biggest and most exciting financial market in the world. Whether you sell EUR 100 to buy US dollars at the airport or a bank exchanges 100 million US dollars for Japanese yen with another bank, both are FOREX deals. The players on the FOREX market range from huge financial organizations, managing billions, to individuals trading a few hundred dollars.
Currency speculation is considered a highly suspect activity in many countries.[where?] While investment in traditional financial instruments like bonds or stocks often is considered to contribute positively to economic growth by providing capital, currency speculation does not; according to this view, it is simply gambling that often interferes with economic policy. For example, in 1992, currency speculation forced Sweden's central bank, the Riksbank, to raise interest rates for a few days to 500% per annum, and later to devalue the krona.[85] Mahathir Mohamad, one of the former Prime Ministers of Malaysia, is one well-known proponent of this view. He blamed the devaluation of the Malaysian ringgit in 1997 on George Soros and other speculators.
Foreign exchange fixing is the daily monetary exchange rate fixed by the national bank of each country. The idea is that central banks use the fixing time and exchange rate to evaluate the behavior of their currency. Fixing exchange rates reflect the real value of equilibrium in the market. Banks, dealers, and traders use fixing rates as a market trend indicator.
The forex market consists of trading pairs of international fiat currencies pegged against each other where traders speculate and hedge risk on the price of a specific national currency appreciating or depreciating relative to another currency. Interestingly, there is no central forex exchange, and all trading is open 24 hours a day, more than 5 days a week, with OTC financial trading centers operating in major cities around the world.
It’s great having an effective once a day trading method and system. However, even a consistent strategy can go wrong when confronted with the unusual volume and volatility seen on specific days. For example, public holidays such as Christmas and New Year, or days with significant breaking news events, can open you up to unpredictable price fluctuations.
"There is a very high degree of risk involved in trading securities. With respect to margin-based foreign exchange trading, off-exchange derivatives, and cryptocurrencies, there is considerable exposure to risk, including but not limited to, leverage, creditworthiness, limited regulatory protection and market volatility that may substantially affect the price, or liquidity of a currency or related instrument. It should not be assumed that the methods, techniques, or indicators presented in these products will be profitable, or that they will not result in losses." Learn more.
The forex market is divided into tiers based on the amount of money being traded. The upper layer consists of major commercial banks and securities dealers, who account for 51 percent of all transactions in the market. Citigroup Inc. is the leading currency trader in the foreign exchange market, accounting for 12.9 percent of the overall market in 2016.

Once Nixon abolished the gold standard, the dollar's value quickly plummeted. The dollar index was established to give companies the ability to hedge this risk. Someone created the U.S. Dollar Index to give them a tradeable platform. Soon, banks, hedge funds, and some speculative traders entered the market. They were more interested in chasing profit than in hedging risks. 

The need to exchange currencies is the primary reason why the forex market is the largest, most liquid financial market in the world. It dwarfs other markets in size, even the stock market, with an average traded value of around U.S. $2,000 billion per day. (The total volume changes all the time, but as of August 2012, the Bank for International Settlements (BIS) reported that the forex market traded in excess of U.S. $4.9 trillion per day.)