The biggest difference between hunters and jumpers is the way they are judged.
Hunter horses are judged on the way they move, their physical appearance, their style on the jump but also their gaits and conformation. on the contrary, jumpers are only judged on the fences down and the time used to finish the course.
To summarise, a hunter horse has to be pretty, move well, be elegant and round above the jump. The jumper must not touch the poles and be fast.
Hope this helps :)
A Hunter, is a horse that competes in the hunters, and the Hunters is when the horse is being judged on how well it moves, the striding between the fences, and how constant the course is done. A Jumper, is a horse that competes in the Jumpers, which is where there is no judges, but it is based on speed and not knocking down any of the jumps!