A smallish, furry,
sentient warrior race living on the forest moon of the planet
Endor. Completely underestimated by the
Empire, both on the basis they were
non-human and the basis that they were teddy-bear-esque and harmless-seeming. However, they sided with the
Alliance and were *the* key in aiding the
Rebels with the destruction of the
shield generator, which allowed the pilots to destroy the second
Death Star.
The Ewoks are a hunter/gatherer culture with a very close-knit clan structure. Their spirituality is based around life-energy and especially trees. A tree is planted for each Ewok at his or her birth, and there is a special binding between Ewok and tree. The shaman or medicine man is one of the highest-up in the tribe, revered even above the war-leader (chief). The elders are also active in tribe government.
On a completely different note, George Lucas had origianally planned on populating the Forest Moon with Wookiees, but decided that after having depicted Chewbacca as he did in the previous two movies, there was no way the Empire could consider the Wookiee people harmless. So he chopped them in half, made them cuddlier and seemingly more harmless, chopped the *name* in half, switched sylables (Wook-iee, E-wok) and got the Ewok species. The Ewok language was actually created by a linguist, it is predominantly Swahilii spoken backwards. Additionally, Warwick Davis, Wicket the Ewok, was originally a supporting character only but was made lead Ewok when it was realized he had the easiest time pronouncing the language through the awkward configurations of the mask.