You have an S3 and a P4 and have no clue....Wow...
It's early and I need a few secs to blow so here goes...
172, 170 are the crank length...Thingy that your pedal screws in that you turn to make your bike go...
11s, 12s....Number of teeth on the rear cassette...28 gives you a higher gear that makes it easier to spin going up hill...11 will allow you to go faster on the flats, assuming you can push the gear...
Ride, train and read...