ChildWin is the class for moveable windows that are children of the main window of an application. The ChildWin for an application is typically the document window.
On Windows, ChildWin is an MDI (multi-document interface) child window, which can be maximized, minimized, and resized within the main window. Typically, ChildWin windows have a system menu.
In the declaration for a ChildWin, you can specify the wInvoke variable, to provide the menu, menu item, or pushbutton used to invoke the window (used by the Invoke method).