This is a proplyd. It is the embryo of a star. All the gasses had combined in the nebula to form the proplyd.
This is a nebula. It is combo of all interstellar gases. These gasses form a star and where stars form.
This is a protostar. The protostar is in the early stages of the star being formed. It is still gathering more mass and gas to form a stable star.
This is a main sequence star. It is at its calmest stage of its life. The gravity and pressure is perfect so it is stable. As the years go by the older it becomes, uses more gasses and eventually can turns into a different star. Such as a red giant.
This is a re giant. It is almost at its final stages of a star. It will be about a few billion year old at this stage. It eventually will die very quickly due to the amount of fuel being used.