What is the difference between a planet and a planetoid?

Answer 1

Note that this is purely arbitrary :

A planet's orbit should be more circular,

and it must be massive enough to have cleared most of the stray material near its orbit.

Note that these are the main reasons why Pluto got demoted.

Answer 2

A planet is a celestial body that orbits a star, has cleared its orbit of other debris, and is large enough to be round due to its own gravity. A planetoid, also known as a dwarf planet, is similar to a planet but has not cleared its orbit of other debris and is not as massive as a planet.