|Artist's concept courtesy of|
Another name given to Pluto, one of the largest examples of this type of body, is an ice dwarf. Ice dwarfs are "planetary embryos" and the Kuiper Belt is full of them. Pluto is also doing something no other body outside the comets does. It is shedding atmosphere like a comet and New Horizons will hopefully find out why. The long endurance probe is also hopefully going to shed light on comets that come in and give Earth a swat from time to time so we can learn a little more about that as well.
If all goes well, I have heard there is thought being given to finding another target to explore once New Horizons passes Pluto. This should get interesting out on the icy frontier. Stay tuned for next summer. It'll be some cool viewing on those hot, sultry days in July.