With the recent news of killer asteroids exploding over Russia and slipping inbetween communication satellites, I have heard a lot of people misusing the terms to describe space junk. There are many different classifications of space debris.
A meteoroid is a piece of space debris that could range from the size of a grain of sand to the size of a large boulder. Any type of space debris larger then a meteroid is considered an asteroid. Once a meteroid enters the Earths atmosphere it becomes a meteor, or shooting star. As the rock starts to break off and get hotter and hotter, the dust that breaks off leaves a bright streak of light in the sky. If the meteor becomes bright enough, it will be classified as a fireball, a meteor that has a magnitude of 3 or more. If the meteor survives the extreme temperatures it gains during entry and the impact with the surface, it becomes a meteorite.