What is margin?

Initial margin is what it takes to open the position. Maintenance margin is the minimum the exchange requires to keep it open. When losses push your margin below the maintenance level, the position is liquidated.

Isolated margin limits the collateral at risk to what is assigned to one position. Cross margin lets every position draw on the whole account balance, which can delay liquidation but put more of the account at risk at once.

Knowing which mode you are in is part of checking total exposure.