The best explanation that I've heard for what Hell is, comes from a sermon by John Burke, the author of Imagine Heaven.

In this sermon, Pastor Burke teaches that God created angels and before our universe. Angels were created to love and serve and therefore required free will since it's not possible to truly love without the capability of not loving and serving without choice is slavery, which a good and just God would not do. The most powerful and beautiful angel was Lucifer (light-bearer) who became prideful and thought he could rise above God. For the sin of pride, God cast Lucifer from Heaven. One third of the angels left Heaven with him. Burke claims that choices made in eternity are eternal choices since there is no time there. Lucifer and his angels wanted to rule apart from God, but since God is everywhere, there was no place for them. So, God, in his love, created Hell, a place without God, for them to rule in.

In order to teach the remaining two-thirds of angels in heaven not to rebel, he created our universe which contained a fraction of heaven and a fraction of hell. This allowed humans to experience both existences (knowledge of good and evil) though not at full strength. He also gave us Jesus, so that we could repent at any time during our life here in time before we have to make the final eternal choice of one or the other.

Burke cites three chapters as his source (“something close to the story that I just told you”):

• Ezekial 28
• Isaiah 14
• Revelation 12

I must admit that I don't read all of what he says in those three scriptures, but I have always tended to be more of a literalist and have always had trouble reading “deeper meanings” or allegory in what I read. I do like his explanation though.

If you can get behind John Burke's interpretation above, Hell is just a place where God is absent and is therefore not responsible for how it is run. So, Hell at a minimum is a place run, or at the very least inhabited by, the very worst of humanity. More likely, it is run by Satan and his demons, who encourage all sinful human behavior, so it would indeed be a pretty terrible place.

C.S. Lewis said that Hell was a self-imposed isolation from God. This seems to agree at least in part with Burke's description above. In essence, Lewis's view of hell is not a place of fiery torment, but rather a state of being characterized by separation from God and self-imposed isolation. It is a consequence of free will and the choices individuals make in their lives.

This view has basis in scripture (2 Thessalonians 9-10 NASB): These people will pay the penalty of eternal destruction, away from the presence of the Lord and from the glory of His power, when He comes to be glorified among His [h]saints on that day, and to be marveled at among all who have believed—because our testimony to you was believed.

However, Jesus describes Hell as a “furnace of fire” (Matthew 13:41-42): The Son of Man will send forth His angels, and they will gather out of His kingdom [y]all stumbling blocks, and those who commit lawlessness, and they will throw them into the furnace of fire; in that place there will be weeping and gnashing of teeth. And Revelation references a “lake of fire” (Revelation 13:20) And the beast was seized, and with him the false prophet who performed the signs [h]in his presence, by which he deceived those who had received the mark of the beast and those who worshiped his image; these two were thrown alive into the lake of fire, which burns with brimstone.