Hello Caliboy.
AF-S is single autofocus mode, while AF-C is continous mode. If you shoot action, you should set your camera to AF-C as you will be able to follow the moving object you want to shoot. If you got one of the fast AF lenses i.e. the 70-200mm VR, you will experience a huge difference.
Best regards
Klaus
http://www.hertz-ladiges.com