A context provides the setting for graphics operations within Screen. All Screen API objects, with the exception of events, are created within the scope of a context and access to these objects is always with respect to the context associated with the object. Through using a handle to a context, you can identify and gain access to the certain Screen API objects (e.g., windows, groups, displays, pixmaps) to set or change their properties.
For more information, see Screen context types.