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. Lucifer is the ruler of hell.

Demon powers
Super strength 

Invulnerability 

Enhanced speed (Alastair and Lucifer)

White light demon blast (Lilith)

Super endurance and stamina

Telekinesis 

Pyrokinesis (Lucifer and Azazel)

Known inhabitants
Lucifer (Ruler)

Azazel (Lucifer's son)

Alastair and his parents

Meg

Ruby

Hellhounds (demon dogs)

Lilith

(Alastair's subordinates)

Dean 

Castiel (Castiel went to Hell to save Dean)