You may receive a Margin Call when your available equity drops below the required level to maintain your open positions. A Margin call comes into effect when your Margin level % drops below 100%.
When this occurs you can't open any new positions whilst closely monitoring your open positions, managing and minimising losses. Alternatively, you can top-up your account balance.
An Auto Margin Close-out will occur when your Margin Level % reaches 50%. Your biggest "negative trades" will close-out first until your Margin Level % reaches 100%.