An immense collection of very light elements. A star is over 95% hydrogen with trace amounts of helium,
oxygen, carbon, and other
heavy elements. The star derives its energy from a thermonuclear reaction initieted by the pressure created by the gravitational pull of the gasses inward. A star will burn for millions if not billions of years before the hydrogen supply is depleted and the star's nuclear fusion reaction fails. The star will then explode and remove an outer layer of gasses and then collapse into a dense state. Average stars collapse into Dwarf Stars while
massive ones form neutro stars of black holes.