Stages of a Star Red Giant/Supergiant

During main sequence, a star is using hydrogen as its fuel for nuclear fusion. Eventually a star runs out of hydrogen and instead begins burning helium. As helium burning begins the center of the star becomes more compact. The outer part of the star expands out further than it ever has before. The result is a star that is often called a Red Giant or Red Supergiant.

The results of a red giant can be devastating on a solar system, as you will see on the next page.

Source
http://aspire.cosmic-ray.org/labs/star_life/starlife_after.html (fair use)