Pluto is neither a planet nor a moon. Moons are objects in space that orbit around a planet, like Earth's Moon, or Phobos and Deimos, which orbit Mars. Planets are objects in space that orbit around a star, like our Sun. However, there are lots of objects that orbit the Sun, so we only call really big objects planets. Pluto used to be considered a planet, but it isn't quite as big as the rest of the planets, and it also orbits the Sun in a really weird orbit. Because of this, astronomers recently decided to not call Pluto a planet anymore - it is now considered a dwarf planet.