In a perpetual contract, the full margin and the cross margin are the ways in which the user needs to pay the margin when opening or closing a position.
Full margin refers to the user needing to pay the margin for all positions when opening or closing a position. This means that if the user has multiple different positions, they need to pay the margin for all positions when opening or closing. The advantage of this method is that the user can get a lower leverage because they can open a position with less margin.
Cross margin refers to the user only needing to pay the margin for each position when opening or closing a position. This means that if the user has multiple different positions, they only need to pay the margin for each position when opening or closing. The advantage of this method is that the user can get a higher leverage because they can open a position with less margin. However, this method also has risks because if the value of a position falls, the user may face the risk of having to add margin. For example, a trader opens a BTCUSDT position. When the BTCUSDT position is liquidated, he will lose all of his USDT balance. BTC balance will not be affected.