Leverage simply allows traders to control larger positions with a smaller amount of actual trading funds. In the case of 50:1 leverage (or 2% margin required), for example, $1 in a trading account can control a position worth $50. As a result, leveraged trading can be a "double-edged sword" in that both potential profits as well as potential losses are magnified according to the degree of leverage used.
In the world of trading, it means you can access a larger portion of the market with a smaller deposit than you would be able to via traditional investing. This gives you the advantage of getting greater returns for a small up-front investment, though it is important to note that traders can be at risk of higher losses when using leverage. In finance, it is when you borrow money, to invest and make more money due to your increased buying power. Once you return what you borrowed, you are still left with more money than if you had just invested your own capital.
400:1: Four-hundred-to-one leverage means that for every $1 you have in your account, you can place a trade worth $400. Some brokers offer 400:1 on mini lot accounts but beware any broker who offers this type of leverage for a small account. Anyone making a $300 deposit into a forex account and trying to trade with 400:1 leverage could be wiped out in a matter of minutes.
When you trade forex, you're effectively borrowing the first currency in the pair to buy or sell the second currency. With a US$5-trillion-a-day market, the liquidity is so deep that liquidity providers—the big banks, basically—allow you to trade with leverage. To trade with leverage, you simply set aside the required margin for your trade size. If you're trading 200:1 leverage, for example, you can trade $2,000 in the market while only setting aside $10 in margin in your trading account. For 50:1 leverage, the same trade size would still only require about £40 in margin. This gives you much more exposure, while keeping your capital investment down.