Every graphical Win32-based application creates at least one window, called the main window, that serves as the main window for the application. This window serves as the primary interface between the user and the application. Most applications also create other windows, either directly or indirectly, to perform tasks related to the main window. Each window plays a part in displaying output and receiving input from the user.
When you start an application, the system also associates a taskbar button with the application. The taskbar button contains the program icon and title. When the application is active, its taskbar button is displayed in the pushed state.