"And I saw thrones, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God, and which had not worshipped the beast, neither his image, neither had received his mark upon their foreheads, or in their hands; and they lived and reigned with Christ a thousand years. But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection. Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years." (Revelation 20:4-6)
The first resurrection is a spiritual resurrection. It pertains to those who have been judged worthy to be with Christ Jesus once they pass from this life. So it has to do with now--this moment! None of us are guaranteed a tomorrow; nobody is guaranteed even two hours from now! It's highly unlikely, but a plane could crash into my room two hours from now--killing me while I sit here at my computer. We must decide right now if we are going to do truth--thereby coming to the light; or are we going to do evil--thereby showing that we hate the light, thus turning from it. The decision--that determines our eternal dwelling place--needs to be made now. I suspect that not all Christians of the past and who are living now have partaken/will partake of the first resurrection. And I also suspect that there are some who were not/are not known as being Christians but have been resurrected the first time. Eternity for everybody begins at this moment, now.
The thousand years is not in the future. And the first resurrection is not a physical resurrection of the just (that happens at the beginning of this future thousand years). Likewise the second resurrection is not a physical resurrection of the unjust only (that happens at the end of the future thousand years). This is a wrong teaching that has permeated the church. Its popularity apparently has to do with the rapturist/futurist/pre-millenialist model for interpreting the book of Revelation and all the other prophetic passages in scripture--by the way, an eschatological model that lends itself to Zionism.
Now the second resurrection is a physical resurrection of everybody. It will happen at the end of the thousand years, which is signaled by the second return of Christ Jesus to establish his kingdom here on earth literally. Some (of those who have died or fallen asleep) will be raised to everlasting life; others (of those who have died or fallen asleep) will be raised to everlasting contempt. The latter will be cast into "outer darkness," where they will weep and gnash their teeth--contemplating their decision to reject the True God. The former will be the ones who took part in the first (spiritual) resurrection. Those who are alive at Jesus' second coming--and who are also counted among the just--shall not precede those saints who have fallen asleep (in receiving their glorified bodies)--as 1 Thessalonians says.
Revelation 20:12-15 says this: "And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works. And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works. 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." The second death is a spiritual death as well as a physical death--in the sense that the unjust shall be physically far away from Christ. For the first death is a spiritual death: it does not denote the life breath leaving the body, a condition that we know as death: it happens in this life. Meaning, it is how somebody ends the life that they live now. Will they be counted among the righteous or among the unrighteous? All will enter the kingdom of God, but the question is: will a person be close to Christ Jesus or will they be far away. The unjust may have an opportunity to move closer to Christ, but first they must be enlightened--a process that seemingly will occur in the eternity to come.
The first resurrection is spiritual and leads to everlasting life; whereas the first death is also spiritual and leads to "eternal damnation" (the second death). Everlasting life is to be with Jesus Christ forever. The second death is to be separated from God forever. It does not mean burning in hellfire for all eternity. The lake of fire is not a literal lake of fire. It will be a place that is a torment of the mind: people who end up there will be thinking about why they turned away from the truth when they were in this life. They will have resurrected (glorified) bodies like the just, but they will be far away from the presence of Jesus Christ. Note also that hell will be thrown into the lake of fire. For hell is a temporary holding place for sinners who did not repent and turn from their wicked ways to the truth. Those who are in hell right now are awaiting the second death--that is they are waiting to receive their new bodies in the second resurrection (of all who've died), after which they are to be judged righteously and thrown into outer darkness. But in the temporary place of punishment (hell) the wicked have no bodies, so they cannot feel pain in the physical sense. The body is asleep in the grave. The breath of life (the spirit) has returned to the Father, from whom it came. The soul--being the union of the mind and the body--has been split, so to speak. It appears that that part of the soul--that is one's true essence--if he or she be wicked, is put in hell or "gehenna" (a name originally referring to the valley of Hinnom, which was just outside of Jerusalem to the south, where the city's trash was thrown out). So gehenna (hell) should be a place to be avoided after death--by showing mercy to others and doing judgment in this life.
Luke 16 has a story about the rich man and Lazarus. Lazarus died and went "into Abraham's bosom." (verse 22) The rich man also died, but he ended up "in hell." (verse 23) He speaks of being tormented in flame and learns from Abraham that there is a "great gulf" preventing Lazarus from coming over to him give him relief--by cooling the rich man's tongue with one of Lazarus' fingers dipped in water. Thus neither can someone in hell pass over to the other side--where Lazarus is comforted. Then the rich man asks Abraham to send Lazarus back to warn his "five brethren" who are still alive, that they might not end up in hell with him. Abraham assures him that only hearing the prophets can his brethren save themselves from such a future; Lazarus coming back from the dead to speak with them will not convince them to repent and turn to the truth. The rich man is conscious of his situation. He is not, however, conscious of the world of the living. He still believes that his brothers are alive. They may have died also for all he knows. As we can see in 1 Samuel 28:14-15, Saul has gotten the witch of Endor to call up the by then deceased Samuel from the underworld, but not from the same compartment that the rich man is in. And Saul informs him that he is being severely pressured by the Philistines. Now as for the rich man he is being tormented not by actual fire but by the metaphysical fire of a guilty conscience, if you will.
We can speculate about where hell is. It may be at the very center of the earth, which is why we call it the underworld because it is literally beneath our feet but yet also in another dimension (vibrates at a frequency that we cannot perceive with our eyes)--"sheol" being another name for the underworld. For it is likely that if you could--by way of a giant earth-drilling vehicle--burrow through the earth's crust into the inner earth (where the nephilim live), you will encounter a different dimension--a different plane of existence. And at the very center--the central sun within the earth--is hell. (The earth's central sun (at its core) and the sun--that the planets of our solar system revolve around--are not what they seem: one accepted as being a ball of molten metal and the other a ball of plasma. The nature of both suns is something all together different: electric.) So the sun at the earth's center is a place of yet another dimension different from that of the surrounding inner earth (which is different from the 3rd dimension that we inhabit here on the surface). Hell is in the earth's central sun, where the consciousness of the wicked reside, but not physically. It is said that crystals deep within the earth are used as containment units for the spirits of the dead nephilim. Demons are the disembodied spirits of the nephilim who wander the earth's surface--in contrast to angels who do have bodies. And the demons can be sent to hell, as witnessed by Mark chapter 5 where a demon named Legion (actually many demons) implores that Jesus not "torment" them. Jesus honors their request to be sent into a herd of nearby swine, but the swine end up committing suicide by running "down a steep place into the sea..." (verse 13)
Paul said this to the brethren in Philippi: "For to me to live is Christ, and to die is gain. But if I live in the flesh, this is the fruit of my labour: yet what I shall choose I wot not. For I am in a strait betwixt two, having a desire to depart, and to be with Christ; which is far better..." Here he speaks of being consciously with Jesus Christ after he dies--his body falls asleep.
King David said something revealing about the afterlife: "But now he is dead, wherefore should I fast? can I bring him back again? I shall go to him, but he shall not return to me." (2 Samuel 12:23) David was saying that his infant first son with Bathsheba had died and that once the time comes when he too will die, he will be able to be with him: again, another verse suggesting a type of consciousness after the body enters into a state of sleep.