a region of icy bodies that lies far beyond the orbit of Neptune – which at 4.5bn kilometres from the sun is the most remote planet in the solar system.
What makes a dwarf planet a dwarf planet and not an asteroid? Don't they both orbit the sun? Is it based on size?
Size matters.
A dwarf planet is a planetary-mass object that is neither a planet nor a satellite. More explicitly, the International Astronomical Union (IAU) defines a dwarf planet as a celestial body in direct orbit of the Sun[1] that is massive enough for its shape to be controlled by gravitation, but that unlike a planet has not cleared its orbital region of other objects.
http://en.wikipedia.org/wiki/Dwarf_planet