Since the discovery in 1992 of a large population of objects beyond Neptune by Dave Jewitt and Jane Luu that it became clear that Pluto was not alone as a strange, small planet.
Pluto is a member of the Kuiper belt, which is a donut-shape region just outside of Neptune populated by several icy leftovers from the formation of the planets. These objects have sizes of 10 to a few 1000 km and Pluto is one of the largest ones.
Whether Pluto is or is not a planet is a matter of definition. According to the currently accepted definition, it is not a full blown planet. But it falls into the intermediate category of “dwarf planet”.
New Horizons is about 100 million km away from Pluto, approaching it at about 15 km per second (that gets you from London to Paris in 24 seconds). At the press conference, the team will probably show slightly more detailed images than those from April 14. In those we could already tell that Pluto and Charon (its moon) have different appearances, both in colour and reflectivity (Pluto is shinier.)
In about 2.5 to 3 months, New Horizons will fly past Pluto and certainly report very interesting findings about this distant world. Then, it will continue on its path, going by at least one more of the objects in the Kuiper belt, a much smaller one, about 100 km in size. Personally, I am very interested to see what that smaller object looks like. Those objects are very much like baby planets that can tell us about how the 8 planets of the solar system formed.