What does the equity represent?

The Equity represents the state of your account if you were to close all of your open positions. It includes the account balance + used margin + unrealized profits and losses.

The 'used margin' is the allocated or invested funds being traded in open positions, or in pending orders. 

Please note, the Equity does not include deductions due to spread. 

Cash equity, on the other hand, is the total value of the unrealized real funds.