Balance - the value of your account before considering any current open positions.
Equity - This would be the current value of your account if all current positions were closed.
Margin - The amount of money you need to have, and maintain, in your account to cover any open positions.
Free Margin - The difference between your Equity and the Margin amount above.
Margin Level - This is the ratio of Equity to Margin, calculated by the following formula:
(Equity / Margin) x 100 = Margin Level