Muggles' Guide to Harry Potter/Magic/Centaur

Overview
Centaurs are magical creatures with the upper body of a man and the lower body of a horse.

Extended Description
Centaurs are a noble race that greatly values astrology and Divination. They like to keep to themselves, and think that it is beneath them to do a wizard's bidding. There is a large herd of centaurs that lives in the Forbidden Forest around Hogwarts. They are excellent archers. Notable Centaurs include Firenze and Bane; Magorian and Ronan are also mentioned.

Centaurs do not like to associate with humans, but they "do not harm foals" (meaning children and teenagers). They also do not like being underestimated or thought of as creatures. They attack Professor Umbridge after she calls them "filthy-half breeds" and states they have "near-human intelligence." They also get extremely angry at Hermione for letting on that she and Harry had purposefully led Umbridge into the forest so the Centaurs could "take care of her for them."

Analysis
Centaurs see themselves as more intelligent and more aware of the world and the Universe than humans; this is why the more excitable among them, notably Bane, get so angry when their intelligence is impugned by "mere Humans". Firenze is expelled from the herd because he chooses to work for Professor Dumbledore, as the majority of the herd feel that this makes him subservient to a human.