In Microsoft HTML Help, the Help window is a combination of the standard Help window with the added functionality of an Internet browser. The window is called the tri-pane window because it contains three panes:
The left pane contains the Contents, Index, and Search tabs to help users move around the system.
The right pane contains the selected HTML Help topic.
And the top of the window has navigational buttons to help the users move through the Help system.
You can revamp the window to suit your needs, as well as add your own custom windows.