CFrameWnd
Frame windows are windows that frame an application or a part of an application. Frame windows usually contain other windows, such as views, tool bars, and status bars. In the case of CMDIFrameWnd, they may contain CMDIChildWnd objects indirectly.
CDocument
A document represents the unit of data that the user typically opens with the File Open command and saves with the File Save command.
CView
represent the client area of a frame window. Views show data and accept input for a document.
A view class is associated with a document class and a frame window class using a document-template object.
CDocTemplate
Document-template objects coordinate the creation of document, view, and frame window objects when a new document or view is created.
CMDIChildWnd
An MDI child window looks much like a typical frame window, except that the MDI child window appears inside an MDI frame window rather than on the desktop. An MDI child window does not have a menu bar of its own, but instead shares the menu of the MDI frame window. The framework automatically changes the MDI frame menu to represent the currently active MDI child window.