Also, the truck height can vary. If you get a set of trucks that are particularly high, you can use larger wheels, but you'll also be higher off the ground.

Finally, the axle length of trucks varies. This is so that you can match your truck size to your board. You'll want your trucks to be within 1/4" of the size of the deck.

For a beginner, I would recommend a basic set of trucks that match the size of your board, along with medium bushings. But don't worry too much about this -- bushings are easier to change than the whole truck. Just match up the right size at first, and you'll be fine.