There actually is a difference between hunters(also refered too as equitation classes or simply 'eq' classes) and jumpers.
Like what StormyBlues said in hunters you want the judge to think "Man, I'd love to ride that horse" You want everything to look pretty and perfect for both you and your horse..
Also in hunter classes the types of jumps are a lot more traditional looking.
Now jumpers is a WHOLE different story, and in my opinion a lot more exciting too
In jumperc classes it doesn't matter what you look like (to a certain point of course, you still want the correct leads and all that jazz) as long as you're fast, and leave all the rails up and not knock any down. There is a set time limit you have to stay within and the more rails you knock down the more time you get added onto your final time.
[still with me? :)]
Also in jumpers if doesn't matter if you 'knick' or 'chip' a rail, as long as it stays up, you're good. However, in hunter classes, chipping is frowned upon.
The types of jumps in jumper classes are a lot more fun and bright colored!
Even the wardrobe is different. In jumper classes usually one wears a nice polo shirt and white breeches. And the hunter classes wear traditional show clothes with beige breeches and a show coat.
I hope that didn't confuse you too much, if you have any questions feel free to ask!