CWinApp is an application object provides member functions for initializing your application (and each instance of it) and for running the application.
Each application that uses the Microsoft Foundation classes can only contain one object derived from CWinApp. This object is constructed when other C++ global objects are constructed and is already available when Windows calls the WinMain function, which is supplied by the Microsoft Foundation Class Library. Declare your derived CWinApp object at the global level.
When you derive an application class from CWinApp, override the InitInstance member function to create your application's main window object. 
In addition to the CWinApp member functions, the Microsoft Foundation Class Library provides the following global functions to access your CWinApp object and other global information: 

AfxGetApp Obtains a pointer to the CWinApp object.
AfxGetInstanceHandle Obtains a handle to the current application instance.
AfxGetResourceHandle Obtains a handle to the application's resources.
AfxGetAppName Obtains a pointer to a string containing the application's name. Alternately, if you have a pointer to the CWinApp object, use m_pszExeName to get the application's name.   _{Your Comment}