Because there is a massive amount of confusion over it, the sun is a several thousand degree hot natural fusion reactor fusing hydrogen atoms into helium atoms at a rate of 620 million metric tons of hydrogen every second. It outputs the energy released largely in the form of light and neutrinos. It was formed when nearby supernovae triggered the gravitational collapse of a molecular cloud, causing it to gain enough concentrated mass to begin nuclear fusion; the remnants of the cloud were subsequently blown away and formed planets, comets, moons, and various other bits of dust and rock in the solar system.
Stars are also naturally occurring hydrogen fusion reactors, formed from the gravitational collapse of a molecular cloud, which output much of their produced energy in the form of light and neutrinos. Their excess material and dust was blown away to form planets, moons, and various bits of dust found in extrasolar systems, much like our sun.
Therefore, the sun is a star.
