The part of your funds that are not in use for open positions.
This includes funds that are used on open orders and pending withdrawals.
Your Cash Balance can never be affected by open positions.
The part of your funds that you have deposited as margin for your open positions.
Your leverage determines the amount of margin that you have deposited on a position. When you increase the leverage, you subtract from your Margin Balance and add to your Cash Balance. When you decrease it, you do the opposite.