According to Wikipedia:
"New Horizons is a NASA space probe launched to study the dwarf planet Pluto, its natural satellites and one or two Kuiper Belt objects, depending on which are in position to be explored."
What is interesting is that the large objects in the Kuiper belt, could be potential future colonies for humanity, after the inner planets have been colonized, and the moons of the gas giants. One of the issues of colonizing one of these objects so far from the sun would be overcoming the immense cold as well as having so little sunlight to grow food with. The New Horizons space probe will help us determine potential candidates.
Source (FutureTimeline) (Wikipedia)