What the Bible says about Hell

Although the Old Testament doesn't say much about hell, there are a few passages that seem to mention it, or something like it.

In Isaiah, God talks about burning people with "everlasting burnings" in a place of immortal worms.

The sinners in Zion are afraid; fearfulness hath surprised the hypocrites. Who among us shall dwell with the devouring fire? who among us shall dwell with everlasting burnings? Isaiah 33:14

And they shall go forth, and look upon the carcases of the men that have transgressed against me: for their worm shall not die, neither shall their fire be quenched; and they shall be an abhorring unto all flesh. Isaiah 66:24

And Daniel says that the dead will someday awake, some to "everlasting contempt."

And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt. Daniel 12:2

But the New Testament fills in the details that were lacking in the Old.

Here's what Jesus had to say about it.

God prepared hell as an everlasting punshment for the devil and his angels, and the people on the left hand of God.

Then shall he say also unto them on the left hand, Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels. ... And these shall go away into everlasting punishment. Matthew 25:41, 46

Someday all the evil dead people will hear Jesus's voice and be damned to hell.
The hour is coming, in the which all that are in the graves shall hear his voice, And shall come forth; they that have done good, unto the resurrection of life; and they that have done evil, unto the resurrection of damnation. John 5:28-29
Hell is a furnace of fire, a place of eternal torment, where there will be weeping and wailing and gnashing of teeth.

The Son of man shall send forth his angels, and they shall gather out of his kingdom all things that offend, and them which do iniquity; And shall cast them into a furnace of fire: there shall be wailing and gnashing of teeth. Matthew 13:41-42

Then said the king to the servants, Bind him hand and foot, and take him away, and cast him into outer darkness, there shall be weeping and gnashing of teeth. Matthew 22:13

And it came to pass, that the beggar died, and was carried by the angels into Abraham's bosom: the rich man also died, and was buried; And in hell he lift up his eyes, being in torments, and seeth Abraham afar off, and Lazarus in his bosom. And he cried and said, Father Abraham, have mercy on me, and send Lazarus, that he may dip the tip of his finger in water, and cool my tongue; for I am tormented in this flame. Luke 16:22-24

It'd be better to cut off your hand or foot, or pluck out your eye, than be cast into the everlasting torment of hell.
If thy hand offend thee, cut it off: it is better for thee to enter into life maimed, than having two hands to go into hell, into the fire that never shall be quenched: Where their worm dieth not, and the fire is not quenched.

And if thy foot offend thee, cut it off: it is better for thee to enter halt into life, than having two feet to be cast into hell, into the fire that never shall be quenched: Where their worm dieth not, and the fire is not quenched.

And if thine eye offend thee, pluck it out: it is better for thee to enter into the kingdom of God with one eye, than having two eyes to be cast into hell fire: Where their worm dieth not, and the fire is not quenched. Mark 9:43-48, Cf. Matthew 18:8-9

According to Second Thessalonians, Jesus will come in flaming fire to punish those who don't know God with the everlasting torment of hell.

In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ: Who shall be punished with everlasting destruction. 2 Thessalonians 1:8-9

And the epistle of Jude says hell will be just like Sodom and Gommorah, except the suffering in hell will be everlasting.
Even as Sodom and Gomorrha, and the cities about them in like manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire. Jude 7
And finally, the last book of the Bible -- Revelation -- explains it all to us. The damned are cast into a lake of fire where they are "tomented day and night for ever and ever."
The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb. And the smoke of their torment ascendeth up for ever and ever. Revelation 14:10-11

And the devil that deceived them was cast into the lake of fire and brimstone, where the beast and the false prophet are, and shall be tormented day and night for ever and ever. Revelation 20:10

And death and hell were cast into the lake of fire. This is the second death. And whosoever was not found written in the book of life was cast into the lake of fire. Revelation 20:14-15