Courtesy of: http://stairways-to-heaven.com/ (Site is no longer available)
The Astral World consist of seven planes, which correspond to the seven divisions of matter; the solid, liquid, gaseous, etheric, super-etheric, subatomic, and atomic. They are as follow:
7th Astral Plane
This is the lowest plane of the astral world, known as Avichi. Here, the lowest, gross and unrestrained passions exist. This plane is hell to the inhabitants who stay here because it’s where desires cannot be satisfied because they do not have a physical body to satisfy them. They can see but they can’t touch! Thus, their inability to satisfy their desires is torturous.
6th Astral Plane
Inhabitants will find themselves in somewhat familiar surroundings, with former family and friends, who often, like themselves, do not realize or refuse to accept the reality that they are dead. Scenery, cities, buildings, furniture, etc. are built by the imaginative minds of the inhabitants.
5th Astral Plane
The inhabitants on the 5th astral plane are busy working out their intellectual desires and ordinary tendencies, tastes, likes and aspirations that they were unable to manifest fully in earth life.
4th Astral Plane
Inhabitants and scenes of people acting out and enjoying their lives that they once enjoyed in earth life. All sceneries and things (including animals) are artificially created by their imagination.
3rd Astral Plane
Dwellers are engaged in work of an inventive and constructive nature. Men and women are perfecting what their interest was while in earth life. For example, artist/musicians creating their masterpieces.
2nd Astral Plane
A great religious atmosphere surrounds this place. Inhabitants of all races, creeds, and beliefs dwell here. Here is where the religious aspirations and emotions find their full power of expression. This is heaven taught by all religions. Imaginative power build up all the scenery here.
1st Astral Plane
This is the highest planes of the astral, inhabited by the great philosophers, scientists and metaphysicians. They were once highly evolved beings who have volunteered from the higher spheres (above the Astral) to teach those here on the highest Astral Plane.
Source: http://stairways-to-heaven.com/7-astral-planes/ (no longer available)