Graphics, Windowing and Events (GWES)
Windows Mobile combines the Microsoft Win32 application programming interface (API), user interface (UI), and graphics device interface (GDI) libraries into the Graphics, Windowing, and Events Subsystem (GWES) module. GWES is the interface between the user, your application, and the operating system (OS).
GWES supports all the windows, dialog boxes, controls, menus, and resources that make up the Windows Mobile user interface (UI), which enables users to control applications. GWES also provides information to the user in the form of bitmaps, carets, cursors, text, and icons.