Here's a breakdown of the terms:

* Meteoroid: A small rocky or metallic body that travels through space.

* Meteor: The bright streak of light we see when a meteoroid enters Earth's atmosphere and burns up due to friction. This is also sometimes called a "shooting star."

* Meteorite: The remaining piece of a meteoroid that survives its fiery descent and actually hits the Earth's surface.

So, the rock itself is called a meteoroid before it enters the atmosphere. When it does, it becomes a meteor, and if it survives and hits the ground, it's a meteorite!