Well one shot is you can't take a picture without the focus being achieved. After every shot you will refocus.
For servo it's good for sports because it is constantly focusing as you half hold the shutter down. So if you move your lens it will focus on that new point. So if you're shooting someone running this will help.
I think that predictive thing focuses where it thinks your subject is going to be if they are moving or something along those lines not too sure.
The last is just plain old let the camera pick where to focus. Usually the closest subject it will focus on. You really don't want to use this so you can take advantage of your camera and get more creative.
Hope that helps!
TJ