Forex. The mainstream business, the biggest market on earth today. It has a daily turnover of more than 2.5 trillion US$ (more than 100 times greater than NASDAQ), and it's still growing. Foreign exchange (FOREX) is the trading of contracts of currency pair exchange rate. It is a NON-DELIVERY trade, which means that there is no physical transaction of currencies, but it is rather an agreement, or "contract" (FOREX DEAL), to trade specific volume of a pair of currencies at an agreed exchange rate. The magnitude of such FOREX trade is that, in order to make the deal, only a proportional amount is needed (the COLLATERAL, or the MARGIN). Thus, if the currency pair exchange rate has changed by some percentage, the value of the MARGIN invested would accordingly change, however - in a much higher proportion. In fact, the actual change onto the Forex trader's investment (the MARGIN they deposited), will be the nominal change occurred to the exchange rate, multiplied by the MARGIN ratio (the leverage).