My understanding has always been that the matador is required to entice the bull around in a "dance" of sorts around the ring. In the process, he stabs the bull in the back with those big dart things which you see sticking out of the bulls back. The idea being that being stabbed with darts will anger the bull and make a better show out of him. I think this is where the matador waves the cape around for a while to tire the bull out. Then, finally, once the matador has "mastered" the bull, he stabs it with the final dart, thus killing it.
I have no idea how close I am to the truth, but that's what I always thought happens.
.....Kelly