Meteors are known commonly as shooting-stars. They are produced by small and friable particles (meteoroids), usually of no more than centimetre size, which do not reach the Earth's surface intact; they may be regarded as cosmical débris, very often of cometary origin. Strictly speaking a meteor is the visible event that occurs when a meteoroid dashes into the upper atmosphere, and is vapourised.

There are many annual well-defined showers, associated with comets, which can often be identified; other meteors are sporadic, not associated with any known comet, and so may appear from any direction at any moment. Meteors can of course occur in daylight, as was pointed out by the Roman philosopher Seneca, about AD 20, and may be tracked by radio and radar.

Meteors are not associated with meteorites, most of which come from the asteroid belt. The link with comets was first proposed in 1861 by D. Kirkwood; he believed that meteors were the remnants of comets which have disintegrated – and in some cases this is true enough. In 1862, G. V. Schiaparelli demonstrated the link between the Perseid meteor shower and the periodical comet Swift–Tuttle, and other associations were soon established.

Some well-known periodical comets are the parents of meteor showers. Halley's Comet produces two, the Aquarids of April and the Orionids of October; Comet P/Giacobini–Zinner can occasionally yield rich displays, as in 1933.