A meteoroid is a body in space which is larger than a grain of dust, but smaller than an asteroid, with meteoroids potentially being roughly boulder-sized. Some meteoroids are in orbit around various celestial bodies, and others move through space until they fall into orbit or collide with an object, which can range from a planet to a space craft. If a meteoroid makes it through the Earth's atmosphere and manages to hit the ground, it is known as a meteorite.
When a meteoroid hits the atmosphere, it generates a bright streak of light caused by vaporizing solids and gases. This streak of light can actually be very valuable to physicists, because spectral analysis of the light provides information about the composition of the meteoroid. The contents of the meteoroid usually vaporize as it moves through the atmosphere, but sometimes part of it survives to hit the Earth, often creating a small impact crater.
Meteoroids are sometimes called falling or shooting stars, since they do look rather like stars which are falling out of the heavens. This is not technically accurate; if a star fell onto Earth, of course, if such a thing were possible, Earth would not survive the collision. This point of fact aside, many people enjoy gazing at the stars and looking for phenomena like meteoroids and passing comets at night when the sky is clear. A sharp-eyed stargazer can spot large numbers, especially during meteor showers, when hundreds may hit the Earth's atmosphere within a few hours.
Aside from being a topic of interest for people who like looking at the starts, meteoroids are also valuable for scientists. Spectral analysis is conducted to learn more about where these pieces of material originated from, and when a meteorite can be recovered, additional studies can be conducted to learn more about it. In some cases, a meteoroid is like a free rock sample from another planet, moon, or other celestial body and it can provide a wealth of information.
A particularly notable meteorite may be retained for display in a museum. Many wind up with scientific institutions which study them and maintain collections of meteorites for the purpose of creating a library of material for research and comparison. Some people have also kept meteorites they have encountered, although laypeople sometimes confuse tektites with meteorites; tektites are actually from Earth, but they melt during a collision and later solidify, sometimes fooling people into thinking they come from space since they are found near impact craters and they look unusual.