A Contract for Difference (CFD) is an agreement to exchange the difference in an instrument’s price between opening and closing a position, without owning the underlying asset. Margin is the deposit needed to open the position, and leverage expresses how large a position that margin controls — for example 30:1 means a small deposit controls a position 30 times larger. Because leverage applies to the full position, it magnifies both gains and losses, which is why margin and stop-out mechanics matter.