An overlapped window is a top-level window that has a title bar, border, and client area; it is meant to serve as an application's main window. It can also have a window menu, minimize and maximize buttons, and scroll bars. An overlapped window used as a main window typically includes all of these components.
By specifying the WS_OVERLAPPED or WS_OVERLAPPEDWINDOW style in the CreateWindowEx function, an application creates an overlapped window. If you use the WS_OVERLAPPED style, the window has a title bar and border. If you use the WS_OVERLAPPEDWINDOW style, the window has a title bar, sizing border, window menu, and minimize and maximize buttons.