Forex and Currency Trading

The foreign exchange market (currency, forex, or FX) trades currencies. It lets banks and other institutions easily buy and sell currencies. 

The purpose of the foreign exchange market is to help international trade and investment. A foreign exchange market helps businesses convert one currency to another. For example, it permits a U.S. business to import European goods and pay Euros, even though the business's income is in U.S. dollars.

In a typical foreign exchange transaction a party purchases a quantity of one currency by paying a quantity of another currency. The modern foreign exchange market started forming during the 1970s when countries gradually switched to floating exchange rates from the previous exchange rate regime, which remained fixed as per the Bretton Woods system.

The foreign exchange market is unique because of
its trading volumes,
the extreme liquidity of the market,
its geographical dispersion,
its long trading hours: 24 hours a day except on weekends (from 22:00 UTC on Sunday until 22:00 UTC Friday),
the variety of factors that affect exchange rates.
the low margins of profit compared with other markets of fixed income (but profits can be high due to very large trading volumes)
the use of leverage

Main foreign exchange market turnover, 1988 - 2007, measured in billions of USD.

As such, it has been referred to as the market closest to the ideal perfect competition, notwithstanding market manipulation by central banks. According to the Bank for International Settlements, average daily turnover in global foreign exchange markets is estimated at $3.98 trillion. Trading in the world's main financial markets accounted for $3.21 trillion of this. This approximately $3.21 trillion in main foreign exchange market turnover was broken down as follows:
$1.005 trillion in spot transactions
$362 billion in outright forwards
$1.714 trillion in foreign exchange swaps

$129 billion estimated gaps in reporting

Market participants

Unlike a stock market, where all participants have access to the same prices, the foreign exchange market is divided into levels of access. At the top is the inter-bank market, which is made up of the largest investment banking firms. Within the inter-bank market, spreads, which are the difference between the bid and ask prices, are razor sharp and usually unavailable, and not known to players outside the inner circle. The difference between the bid and ask prices widens (from 0-1 pip to 1-2 pips for some currencies such as the EUR). This is due to volume. If a trader can guarantee large numbers of transactions for large amounts, they can demand a smaller difference between the bid and ask price, which is referred to as a better spread. The levels of access that make up the foreign exchange market are determined by the size of the "line" (the amount of money with which they are trading). The top-tier inter-bank market accounts for 53% of all transactions. After that there are usually smaller investment banks, followed by large multi-national corporations (which need to hedge risk and pay employees in different countries), large hedge funds, and even some of the retail FX-metal market makers. According to Galati and Melvin, “Pension funds, insurance companies, mutual funds, and other institutional investors have played an increasingly important role in financial markets in general, and in FX markets in particular, since the early 2000s.” (2004) In addition, he notes, “Hedge funds have grown markedly over the 2001–2004 period in terms of both number and overall size” Central banks also participate in the foreign exchange market to align currencies to their economic needs.