What is the difference between a star, planet, and moon?

A star is a ball of gas with enough mass to produce light when it is compressed by gravity and undergoes atomic fusion, which releases energy.

Pluto is not a planet because it is smaller than our Moon, but a planet is defined as a body that, when compressed by gravity, will not generate fusion, whether it is mostly made of rocky or gaseous material and has a stable orbit around a star.

A moon is a rocky celestial body that primarily orbits a planet. Large planets may have moons that would qualify as planets if they orbited their stars.

A planet is a celestial body that orbits a star, is massive enough for its gravity to make it nearly round, and has cleared its orbit of other debris. A moon is a natural satellite that orbits a planet. A star is a celestial body that produces its own light through nuclear fusion.