Moon

A moon is a body that orbits a planet.  Also called a natural satellite. Jupiter has 67 Moons.  Do all Planets have moons? 

Our moon is called Luna.

Q How many moons are in our solar system?

a Planet is 

    a celestial body moving in an elliptical orbit round a star.  There are 8 Planets in OUR solar system.  There are millions of planets. 

It used to be easy to know what was and wasn’t a planet. Planets were big, bigger than any smaller moons that happened to be orbiting them. They were round. They orbited our sun.

Then, in 2006, the erstwhile planet Pluto lost its major planet status, becoming a dwarf planet. 

Around that time, astronomers were discovering a plethora of small bodies in our own solar system, so that there are now half a million known asteroids and over a thousand Kuiper Belt Objects, including five recognized dwarf planets counting Pluto.

Astronomers also now know several thousand exoplanets orbiting other stars.

The dramatic expansion in the number of known objects orbiting our sun and other suns has caused some astronomers to try to override or re-define the 2006 planet definition from the International Astronomical Union (IAU), which caused Pluto to lose full planet status.