The system reduces an application's main window (overlapping style) to a minimized window when the user clicks Minimize from the window menu or the application calls the ShowWindow function and specifies a value such as SW_MINIMIZE. Minimizing a window speeds up system performance by reducing the amount of work an application must do when updating its main window.
For a typical application, the system draws an icon, called the class icon, when the window is minimized, labeling the icon with the name of the window. The class icon, a static image that represents the application, is specified by the application when it registers the window class. The application assigns a handle to the class icon to the hIcon member of WNDCLASS before calling RegisterClass. The application can use the LoadIcon function to retrieve the icon handle.