Frames contain view windows. Frame windows allow the user the capability to use status bars, toolbars, and splitters.
CFrameWnd contains the implementation to perform the function of a main window as wells as it keeps track of currently active view that is independent of Windows active window or input focus. It also provides the functionality of a Windows single document interface (SDI) overlapped. This is contained in CFrameWnd class.
class CFrameWnd : public CWnd