The Level 2 widget is displayed by default in Full View when opening a new Stock tab. 

You may enable or disable the Level 2 widget by using the Level 2 button ()

This will display the Level 2 information for the current stock.

The panel provides real-time information about the quotations of individual market makers and the buy and sell price of a stock. A volume bar is located above the Level II view that shows trades that occurred recently. The height of the bar represents the position size of the trade.