A meteor, like the one seen over Utah on Saturday, is classified as “the streak of light” that you see in the sky when “a small piece of cometary or asteroidal material” enters the atmosphere at high speed and burns up.
The material typically burns up because of frictional heating from the material’s collision with atoms and molecules in the atmosphere.
This is most commonly what occurs. However, when that small bit of comet or asteroid does not completely burn up, and instead makes it to the Earth’s surface, the material that survived the journey is called a meteorite.
Inversely, that same material is called a meteoroid when it has not yet entered Earth’s atmosphere, and is still travelling through interplanetary space.
So, the body of a comet or asteroid “starts its life as a meteoroid,” then makes its fiery streak of light in the atmosphere as a meteor, and if it isn’t destroyed in the process, reaches Earth’s surface as a meteorite!
Diving a little deeper, NASA clarifies the difference between asteroids and comets:
While they’re both planetary objects orbiting the Sun, an asteroid is a “small, rocky object,” which is typically found in a ring between the orbit of Mars and Jupiter called the asteroid belt.
“Some asteroids are round, some are elongated, and some even have a satellite,” NASA states.
When seen in a telescope, an asteroid appears as a point of light.
A comet, however, is composed of ice and dust, and when a comet gets close to the Sun, its ice and dust content starts to vaporize.
“When seen in a telescope, a comet appears fuzzy and/or has a tail,” NASA states.
NASA summarizes the distinctions as such: “Asteroids are rocky, comets are icy, and meteors are much smaller and are the shooting stars that you see up in the sky.”