The key characteristic that distinguishes dwarf planets from planets is their ability to clear their neighborhood of other objects.

Here's a breakdown:

* Planets are celestial bodies that orbit a star, are massive enough to be rounded by their own gravity, and have cleared their orbital path of other objects.

* Dwarf planets meet the first two criteria (orbiting a star and being rounded by their own gravity), but they haven't cleared their orbital path of other objects. This means they share their orbital space with other objects of comparable size.

For example, Pluto, once considered a planet, was reclassified as a dwarf planet because it shares its orbital space with other Kuiper Belt objects.

Let me know if you'd like more details on this!