Personally, I've heard many perspectives on the subject of hell. However, my personal belief on it comes from a book called The Diabolicon. The gist is pretty much that it is basically what you make it to be and that since it is away from god you must make peace in the chaos by yourself. This is pretty much Chaos magick when you think about it knowing that it pretty much makes hell what you believe it is.
In my humble opinion, Hell is just an amalgam of various energies and forces of collective suffering. It exists as a point in reality, much like any non-material realm (astral planes, symbolic planes if they exist), but constituted mainly by a clusterfuckery of disgrace and everything that is miserable about existence. An energetic convergence that, if you go into there, you will be simply in a state of relentless disturbance.
Much like we suckers fell for the incarnation dream, some suckers fall for Hell much like an addict lives miserably in a hellscape of a crack den (like in a guilt trip, for instance). Nobody stays there forever, though, because I don't think anything stands forever. As anything, everywhere, there are alchemic processes to be completed, elements to be created and motives for a soul to be there. As in anywhere.
About demons and devils, I like to view them as the following:
- Demons are entities that concentrates the force of knowledge and the principles of the Gnosis attainable by the alchemic processes of Hell.
- Devils are beings that thrives in Hellish energies and they are assholes, of course. Like that clown (Violator) from Spawn, you know? They're there to laugh at your misery.
I really do believe there are points in reality where the extreme energetic polarities converge into one giant cluster. Hell, Heaven, etc. are what we call these polarities. Some people believe that morality and merit plays some role here, but I don't think so.