What are the stages of a star's life cycle?

All stars begin as a stellar nebula that forms into a protostar. The below stages are for protostars that form into main-sequence stars. The life cycle of a main sequence star depends on the size of the star.

The following stages are for stars that are much larger than our solar system’s Sun. The main sequence star turns into a red supergiant. The red supergiant turns into a supernova. The gases of a supernova serve as the supernova’s fuel. Once the gases are exhausted, the supernova turns into either a neutron star or a black hole.

This second set of stages applies stars that are about the same size as the sun of our solar system. The main sequence star turns into a red giant. The red giant then turns into a planetary nebula, which will eventually become a white dwarf. A white dwarf will theoretically become a black dwarf.