trading on margin gives you more buying power and the potential for more profits (and losses). How does this work, exactly? A 1% margin account allows you to control a currency lot of $100,000 for $1,000. When dealing with $100,000 small changes in the price of the currency can result in large profits or losses. FOREX currencies are traded in much smaller units than cash. The American dollar, for example, is traded in units down to 4 decimal places. Instead of $1.32 FOREX quotes are seen as $1.3256. The smallest unit in FOREX currencies is called the pip, and when you have a $100,000 each pip of your total lot is worth $10 (when trading American dollars).
If the price of American dollars changes from 1.3256 to 1.3356, that's a difference of 100 pips which represents a profit or loss of $1000. Without margin, if you had $1000 of currency, the price change from 1.3256 to 1.3356 represents a difference of $10. Significant to the tourist, perhaps, but not the investor.
So the benefit of margin is increased profit potential.
Risks
As there is increased profit potential, there is also increased loss potential. If you are not careful, your entire margin account could quickly be wiped out. If your margin account is 1% and the currency moves just one cent against you, you lose $1000.
FOREX trading, however, has several methods to limit loss. Stop loss orders automatically close your position if the value of the currency crosses a pre-determined point. Stop loss orders allow you to limit your losses to a specified amount while still allowing potential profit taking.