Here's why:

* Meteoroid: A small piece of rock or metal that travels through space.

* Meteor: A meteoroid that enters the Earth's atmosphere and burns up, creating a streak of light.

* Meteorite: A meteoroid that survives its passage through the Earth's atmosphere and hits the ground.

While the object is in space and before it hits the moon, it's called a meteoroid. Once it impacts the moon, it's just a piece of debris on the lunar surface.