The total portfolio value is a sum of your stock value and the cash you have in your account.
Unsettled Funds is the cash from the sale of stocks that has not yet been cleared as part of the settlement process and as a result cannot be withdrawn. For most stock that are being traded, the overall settlement occurs two business days after the day the order is executed. For example, if you were to execute an order on Monday, it would typically settle on Wednesday.
A capital gains tax is a tax levied on profit from the sale of specific types of assets. This tax is calculated on the positive difference between the sale price and the original purchase price of the stock. Capital gains taxes are only triggered when an stock is sold and are not calculated whilst a stock is held by the investor.