Margin
Margin is the money that trader posts with a broker in order to be able to trade with borrowed capital.
It’s basically the percentage of your overall position that has to be held by your broker (as margin). For example, 25% this money is the same as saying you can trade four times the value of your account. This allows traders to be able to borrow money from a broker while not having to put their capital into a fund that is tied to the underlying assets.