eh...
think you might need to do some reading up on the basics of photography to enhance your understanding....
Shutter priority is when you want to control the shutter speed to get the effect you want... which can range from ensuring that the blades of a helicopter is not frozen in the air, ensuring that the background is blurred while the racing car is sharp, and getting lighttrails from cars at night.
Aperture priority is when you want to control the depth of field in a photo... as in ensuring that the face is sharp while the background is blurred, ensuring that all parts of a scenery is sharp, etc.
Don't think the current Nikon compacts has such modes...