What is meant by the Kuiper Belt?

The Kuiper Belt is a disk-shaped region that exists in the outer solar system, past the orbit of Neptune. It is also known as the Kuiper-Edgeworth Belt. It extends from the orbit of Neptune at around 30 Astronomical Units (AU) out to about 50 Astronomical Units from the Sun. 

It consists of millions of small icy bodies that are thought to be leftover material from the formation of the outer planets. Pluto, Haumea and Makemake are the famous dwarf planets found in this belt.