The IAU (International Astronomical Union) sets definitions for planetary science. According to them, a dwarf planet is a celestial body that:
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,
(c) has not cleared the neighborhood around its orbit, and
(d) is not a satellite.
The “dwarf planet” is a term coined by IAU (International Astronomical Union) in 2006, to explain the celestial objects whose orbit is not clear. It may share a path with asteroids or comets.
As of 2011, the IAU (International Astronomical Union) has officially recognized 5 dwarf planets. They are Ceres, Eris, Haumea, Makemake & Pluto.
It is estimated that there are thousands of dwarf planets yet to be discovered.
The dwarf planets that orbit beyond Neptune are called Plutoids. They exist in Kuiper Belt. As of now, there are 4 plutoids they are Eris, Haumea, Makemake & Pluto.
Ceres is the only dwarf planet to revolve in the asteroid belt of Mars and Jupiter.
The order of the dwarf planet from the sun is Ceres, Pluto, Haumea, Makemake, and Eris.
The largest dwarf planet is Pluto.
The smallest dwarf planet is Ceres.