For questions about luminous spheres of plasma held together by their own gravity, generally comprised primarily of hydrogen and helium.
Stars are massive celestial bodies composed of various elements, mainly hydrogen and helium. They produce energy via nuclear fusion and emit electromagnetic radiation. They may have other objects orbiting them - such as planets, comets, and debris disks - and may even orbit other stars. Questions using this tag should be about the effects of a star on a planet or other body. Also consider planets and astronomy, if they are more appropriate.