Stars do not live forever. Those stars that are bigger than the sun will die along with a explosion called the supernova. The explosion was caused when the centre, the core of the star collapsed. The outer layers are blown off by the explosion, leaving behind the core of the star. The material that flew out of the star may form new stars.
The Supernova last for two years. At this time, the star may shine brighter thaan the galaxy. What happens to the star after thae supernova depends on how big the star was. If the star is jsut a bit bigger than the sun, the core will shrink into a neutron star. If the star is far much bigger than the sun, it will shrink into a black hole.