Lupe. The object is to hit the animal with a very sharp broadhead and cause it to bleed severely and die as a result of that bleeding.
We try to do this in a manner that cause a fairly quick death and also one that leads to a lot of blood loss outside the body and in this way, allow us to more easliy follow the trail of the animal, since arrows do not normally "drop the deer in its tracks" like a bullet might.
There are many "places" where a solid hit could cause the animal's death and several more that might do it.
We try to teach that, in spite of all these "places", you should really be aiming to hit the heart / lung area, for lots of reasons as I am pretty certain will be described by others shortly.
It is arguably the biggest, best, most easily reached area for us to hit with an arrow. A hit here should quickly kill the animal and is also likely to pass completely thru the animal, making a trail a much more sure proposition.
ChuckC