vJoy adds additional virtual joysticks. None of those buttons or axes do anything until you add a program like Joystick Gremlin. Joystick Gremlin can then be configured to use a real joystick output and send it to a vjoy controller. In the example of the twisty stick I mentioned The stick twist output is one axis. With it split by Joystick Gremlin and mapped to vjoy you would have the one axis of the real stick and two axes of vjoy. Twist the stick and the output from both change at the same time. Not a perfect solution but works well enough typically.