Handle to the current instance of the application
Handle to the previous instance of the application. This parameter is always NULL.
If you need to detect whether another instance already exists, create a uniquely named mutex using the CreateMutex function. CreateMutex will succeed even if the mutex already exists, but the GetLastError function will return ERROR_ALREADY_EXISTS. This indicates that another instance of your application exists, because it created the mutex first.
lpCmdLine
[in] Pointer to a null-terminated string specifying the command line for the application, excluding the program name. To retrieve the entire command line, use the GetCommandLine function
谢谢！帮解释下，还有specifying在这段话里我要怎么理解。万分感谢！
