Cash/Margin
A margin account is an account that allows you, the investor, to purchase securities using a combination of cash and credit extended to you from your brokerage firm, optionsXpress. If you do not maintain the $2000 minimum, the account will be limited to the available funds in your account.
Again, no minimum is required to open a cash/margin account, but a $2,000 minimum is required to activate and maintain a margin account.