Margin
Margin is the deposit you put down to open a leveraged position, such as a futures contract, instead of paying the full price. It covers your losses; if it runs out, the position is closed.
With 8,000 of margin on a position worth 80,000, a 1% price move is a 10% change in your deposit. The exchange closes the position, called liquidation, before losses exceed the margin.
Learn more: what is leverage? and how to avoid liquidation.