An asteroid.
A meteorite.
Comets, asteroids, and meteoroids have several similarities. All are small heavenly bodies. All frequently originate in places like the Kuiper Belt and the Oort Cloud and are very small compared to planets. However, differences between the three are clear and easy to establish.
Meteoroids are bits of debris that can range in size from a grain of sand to a boulder; they are not big enough to cause serious, widespread damage should they collide with Earth. When meteoroids enter the earth's atmosphere and create a streak of light in the sky, they are called "meteors." If the meteor is not vaporized in the atmosphere before it hits the ground, the space rock found on the surface of Earth is called a meteorite.
Asteroids are bigger than meteoroids, and can range widely in size. The smallest observed asteroid is 20 feet across, and the largest, Ceres, is 580 miles in diameter. Most of the bodies that we think of as asteroids are (unlike comets) composed of rock. However, the distinction between asteroids and comets is not based on composition; it is based on the presence of a glowing coma or tail. Therefore potential comets orbiting in the Oort Cloud or the Kuiper Belt that have not yet been affected by radition from the Sun are asteroids.
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