Balance is the amount of money on your account after the last closed trade.
Equity is the sum of Balance and current Profit/Loss of open positions and SWAP.
Margin is the amount of money necessary to cover your possible losses during margin trading.
Free margin is the amount availabe to open next trades. Free margin equals equity minus margin.
What is margin call?
Margin Call is an alert to the trader when the account equity falls below 50% Margin Level.
This means,that the account is left with only the supplied margin and should be funded with more money in order to prevent it from facing a Stop Out or a forced closure.
Trading platform will start closing trading positions at Stop Out level, which is set to be 20% of Margin Level.