Hell

Hell in Supernatural, is the place or punishment and pain of the afterlife. Human souls who are sent to Hell are tormented until their humanity is stripped away and they become demons.

Dean spends four months in Earth time in hell, but he reports that time passes differently there, and for him it was more like forty years. This makes 3 days on earth roughly equivelant to a year in hell.

During his time in Hell, Dean was tortured and each 'day' his wounds would be healed, and would offer to stop it, if dean would become a torturer of souls himself. After '30 years' in hell (or 3 months on Earth) Dean accepted the offer and started torturing souls.

Some demons appear to be able to move freely between Hell and the mortal realm eg,. Others are trapped and can only escape through portals such as Devil's gates.

When a demon is exorcised, it returns to hell whereas the and  kills, as in obliterates, the demon and the victim.