A satelite is an object that revolves around an object. The Earth's moon is so named because it revolves around the Earth. So, the moons of a planet are simply bodies of matter that revolve ariund that planet. The Sun is a star. All stars live and die.
Stars produce massive amounts of heat energy and in so doing they also give off light.
The stage of life that a star is in is determined by the colour of light it gives off. The youngest stars are the hottest. They are blue. The youngest stars are the coolest. They are red.