"What is the purpose of the belts the monks wear?"
Belts play a major role in our progression through the different stages of the various martial arts styles that we study. Just as in the martial arts world in the US, Europe, and elsewhere, the belts the monks wear play a very important role. As Shi De Jiang said, when I questioned him about this, for the "official answer", he looked at me with one of those stupid puzzled looks that I tend to get, knowing damn well that I already knew the answer, and said "How else do we keep our pants up?" So much for that. No, rank and such generally is not delineated by belts and the like at the Shaolin temple. Belts, really, when you think about it, are terribly useless things, except if you want to keep your pants up. But, before you get your panties all twisted up about this, I strongly suggest that you read Sensei Eddy Schumacher's excellent discourse on belts and things like that, in "What is Rank?" in the Seidokan section.