A comet is a small celestial body composed of ice, dust, and rocky material that orbit the Sun. Comets typically have a bright, visible coma and a tail of gas and dust. Comets are usually much smaller than asteroids, ranging in size from a few meters to a few dozen kilometers in diameter.
An asteroid is a small, rocky object that orbits the Sun. Asteroids are much larger than comets, typically measuring hundreds of kilometers in diameter. Unlike comets, asteroids do not have a visible coma and tail, so they appear as small, dark objects in the night sky.