**What is it?**
Eternal separation from God. Because God is the source of all joy, eternal separation from Him leads to eternal misery and pain. A soul in Hell is cast away (or more accurately, casts itself away) from God, and is left to the realm of Satan and his minions. This too contributes to the misery of Hell. BTW, as one FReeper tagline points out, Satan is definitely a Democrat!
Where is it?
Good question. This is alot like asking where is Heaven. I really don't know how to answer it - maybe say that both Heaven and Hell exist on other "planes" of reality? They aren't in our space-time - one could not reach Heaven by traveling far enough in a spaceship, or reach Hell by digging deep enough. But they both certainly exist. Heaven has a physical, spatial component as well, for Christ is physically, bodily present there. Don't know about Hell. Of course this all gets tricky, because while God is in Heaven, He is also everywhere in creation, and while Satan is in Hell, he exerts great influence on the Earth. It's fun to speculate about how this all "works" but I'm fairly skeptical that our human minds can ever grasp the truth of the whole thing.
When/for how long? Is it permanent?
Hell is absolutely permanent. To say otherwise is to contradict Christ Himself.
Who goes there?
Anyone who dies who has not repented of his/her sins and accepted the mercy and love of God. I fear that most people, especially in our current world, go to Hell. The gate of Heaven is narrow and few enter it, as Christ says.
Does your pastor/priest/rabbi etc. discuss Hell? The devil? Or is it quietly ignored?
Our priest tries to drive home the importance of Hell, but he has admitted that it is very frustrating at times. So many people have been poorly educated in the faith and so influenced by our secular culture, that they really don't understand the reality of Hell. He worries that what he says just goes in one ear and out the other. At least he tries though. Some priests I've known don't even bother to preach on Hell - wouldn't want to make the congregation uncomfortable, you know :(
Thanks for your reply. I think most of us need a little hellfire and brimstone preached to us now and then.
Do your priests ever speak about the devil? Is Satan perceived to be a reality or a dramatic invention?