This is a star. We'll call him Jim. Jim is a new star, born from a nebula of gas and dust, he has a long life ahead of him to live.
Now Jim here doesn't do much at the moment, he spends his time converting gas into fuel which makes him very bright. Even from far away his luminosity is quite high. Jim is not a very hot star, burning a yellow color. A quite low temperature as yellow is a color on the lower end of the electromagnetic spectrum. Jim is a main sequence star, being very average.
Jim is now much older, he has become a red giant nearing the end of his life cycle. He is very large but also very cool.
end of his life cycle.Jim is now a white dwarf. He is a small white star in the center of a planetary nebula, kind of like where he came from. He has reached the end of his life cycle
Jim could have gone down a very different path if he was born as a massive star. These stars are much brighter and generally higher up on the HR-diagram than main sequence stars like him. At the end of big Jim's life he would me a red supergiant
Afterwards, Jim would either become a neutron star or a black hole. Both are highly dense objects with a large amount of mass. Neutron stars, however, arent as dense as black holes