Hell

Hell is the place evil people go when they die (or sometimes visit when near death). It is run by the Devil, and is the traditional Christian representation; all fire and brimstone.

Homer went there after he sold his soul to the Devil. The whole Simpson family went during the Apocalypse (after Homer stopped Lisa from ascending to Heaven).

The Devil enjoys dealing out cruel and ironic punishments to the denizens of Hell. Homer was fed all the donuts in the world, but didn't take this as a punishment, demanding more donuts. Hell had a poorly-managed barbecue; this succeeded in breaking Homer's spirit.

Canon
Bart had an out-of-body experience which took him there briefly before coming back to life after he had been hit by a car.