A dwarf planet is a celestial body that orbits the sun and is large enough to assume a round shape but has not cleared its orbital path of similar objects. There are five known dwarf planets as of 2014: Pluto, Ceres, Eris, Haumea and Makemake.
The main difference between planets and dwarf planets is that planets are able to clear the neighborhood around their orbits, ensuring that there are no similar objects orbiting in the same zone and at about the same distance from the sun. Dwarf planets are also much smaller than planets. Most dwarf planets are in the Kuiper Belt, a region located beyond Neptune’s orbit.