I believe that the Astral is simply a highway for our souls to travel on. It connects all that is with all there was and will be. It is Past, Present and Future brought together. The Astral might be called a different dimension, or something outside of time and space. As such, it is difficult to describe it as something we would understand as it is not.
It is so vast and limitless that our minds cannot fathom it. Some might say it is actually God, as He is timeless, bodyless and limitless. It will not be possible for anyone to say what it is as it is what you want it to be. God has said in the Bible "I am what I am.". The Astral is what it is. It is there, or it is here it does not matter. Do not trouble yourself with these questions as there is no answer and probably never will be.
May the Light of God guide you.