Hell is a Conspircacy Theory- Proved False, From The Bible, page 1

Gehenna

Symbol of Complete Destruction
Heb., גי הנם (geh hin·nom′, “valley of Hinnom”);
Gr., γέεννα (ge′en·na); Lat., ge·hen′na

“Gehenna” means “valley of Hinnom,” for it is the Greek form of the Hebrew geh hin·nom′. In Jos 18:16, where “valley of Hinnom” occurs, LXX reads “Gehenna.”
The valley of Hinnom lay to the west and south of ancient Jerusalem. (Jos 15:8; 18:16; Jer 19:2, 6) Under the later kings of Judah it was used for the idolatrous worship of the pagan god Molech, to which god human sacrifices were offered by fire. (2Ch 28:3; 33:6; Jer 7:31, 32; 32:35) To prevent its use again for such religious purposes, faithful King Josiah had the valley polluted, particularly the part called Topheth.—2Ki 23:10.

The Jewish commentator David Kimḥi (1160?-1235?), in his comment on Ps 27:13, gives the following historical information concerning “Gehinnom”: “And it is a place in the land adjoining Jerusalem, and it is a loathsome place, and they throw there unclean things and carcasses. Also there was a continual fire there to burn the unclean things and the bones of the carcasses. Hence, the judgment of the wicked ones is called parabolically Gehinnom.”

The valley of Hinnom became the dumping place and incinerator for the filth of Jerusalem. Bodies of dead animals were thrown in to be consumed in the fires to which sulphur, or brimstone, was added to assist the burning. Also bodies of executed criminals, who were considered undeserving of a decent burial in a memorial tomb, were thrown in. If such dead bodies landed in the fire they were consumed, but if their carcasses landed upon a ledge of the deep ravine their putrefying flesh became infested with worms, or maggots, which did not die until they had consumed the fleshy parts, leaving only the skeletons.

No living animals or human creatures were pitched into Gehenna to be burned alive or tormented. Hence, the place could never symbolize an invisible region where human souls are tormented eternally in literal fire or attacked forever by undying worms. Because the dead criminals cast there were denied a decent burial in a memorial tomb, the symbol of the hope of a resurrection, Gehenna was used by Jesus and his disciples to symbolize everlasting destruction, annihilation from God’s universe, or “second death,” an eternal punishment.

Therefore, to have one’s dead body cast into Gehenna was considered the worst kind of punishment. From the literal Gehenna and its significance, the symbol of the ‘lake burning with fire and sulphur’ was drawn.—Re 19:20; 20:14, 15; 21:8.

What's interesting is that death & hell/hades get thrown into it, seems strange, they aren't alive, so they can't die.

Revelation 20 verse 14
International Standard Version (©2008)
Death and Hades were thrown into the lake of fire. (This is the second death-the lake of fire.)

King James Bible
And death and hell were cast into the lake of fire. This is the second death.

How can hell/hades/death have a second death??? They don't.

Gehenna=Lake of fire=Second Death=non-existence with no hope of a return for all eternity.

So when that scripture is fulfilled Hades no longer exists, if somebody dies after this scripture is fulfilled they don't go to Hades, they go into Gehenna which is non-existence, for some it will be literally a second death because they will have come out of Hades only to rebel against God after period of time. That's what John 5 verses 28 & 29 speaks about

28 Don’t be so surprised! Indeed, the time is coming when all the dead in their graves will hear the voice of God’s Son, 29 and they will rise again. Those who have done good will rise to experience eternal life, and those who have continued in evil will rise to experience judgment.
Notice it says "continue in evil", thats right they are not judged on their past sins, only if they persist in evil and bad ways after God brings them back from the grave/hades/sheol will they then go into Gehenna experiencing the second death.

It is permanent destruction of soul and body as Jesus warned about in
Matthew 10 verse 28

Young's Literal Translation
'And be not afraid of those killing the body, and are not able to kill the soul, but fear rather Him who is able both soul and body to destroy in gehenna.

International Standard Version (©2008)
Stop being afraid of those who kill the body but can't kill the soul. Instead, be afraid of the one who can destroy both body and soul in hell.
This is also another example of poor translation as we have clearly shown the difference between gehenna and hades and hell, again this misleads the common bible reader.

Tartarus

“Tartarus”
2Pe 2:4—“By throwing them into Tartarus”
Gr., Tar·ta·ro′sas; Lat., de·trac′tos in Tar′ta·rum;
Syr., ‛a·gen ’e·nun beThach·ta·ya·th
“Tartarus” is found only in 2Pe 2:4. It is included in the Greek verb tar·ta·ro′o, and so in rendering the verb, the phrase “by throwing them into Tartarus” has been used.

In the Iliad, by the ancient poet Homer, the word tar′ta·ros denotes an underground prison as far below Hades as the earth is below heaven. Those confined in it were not human souls, but the lesser gods, spirits, namely, Cronus and the other Titans who had rebelled against Zeus (Jupiter). It was the prison established by the mythical gods for the spirits whom they had driven from the celestial regions, and it was below the Hades where human souls were thought to be confined at death. In mythology tar′ta·ros was the lowest of the lower regions and a place of darkness. It enveloped all the underworld just as the heavens enveloped all that was above the earth. Therefore, in pagan Greek mythology tar′ta·ros was reputed to be a place for confining, not human souls, but Titan spirits, and a place of darkness and abasement.

The inspired Scriptures do not consign any human souls to tar′ta·ros but consign there only spirit creatures, namely, “the angels that sinned.” Their being cast into tar′ta·ros denotes the deepest abasement for them while they are still living. This serves as punishment for their sin of rebellion against the Most High God. The apostle Peter associates darkness with their low condition, saying that God “delivered them to pits of dense darkness to be reserved for judgment.”—2Pe 2:4.

The pagans in their mythological traditions concerning Cronus and the rebellious Titan gods presented a distorted view regarding the abasement of rebellious spirits. In contrast, Peter’s use of the verb tar·ta·ro′o, “cast into Tartarus,” does not signify that “the angels that sinned” were cast into the pagan mythological Tartarus, but that they were abased by the Almighty God from their heavenly place and privileges and were delivered over to a condition of deepest mental darkness respecting God’s bright purposes. Also they had only a dark outlook as to their own eventuality, which the Scriptures show is everlasting destruction along with their ruler, Satan the Devil. Therefore, Tartarus denotes the lowest condition of abasement for those rebellious angels.

In the inspired Scriptures, Tartarus bears no relationship to Hades, which is the common grave of the human dead. The sinful angels and the dead human souls are not associated together in tar′ta·ros as a place of eternal conscious torment of creatures. Tartarus will pass away when the Supreme Judge destroys the rebellious angels presently in that condition of abasement.

2 Peter 2 verse 4
International Standard Version (©2008)
For if God did not spare angels when they sinned, but threw them into the lowest hell and imprisoned them in chains of deepest darkness, holding them for judgment;

Young's Literal Translation
For if God messengers who sinned did not spare, but with chains of thick gloom, having cast them down to Tartarus, did deliver them to judgment, having been reserved,

Again poor translation that misleads.

Sheol

Hades

Gehenna

Tartarus

Abyss