Here is a good explanation by Walter Veight...
'The millennium is the thousand-year reign of Christ with His saints in heaven between the first and second resurrections. During this time the wicked dead will be judged; the earth will be utterly desolate, without living human inhabitants, but occupied by Satan and his angels. At its close Christ with His saints and the Holy City will descend from heaven to earth. The unrighteous dead will then be resurrected, and with Satan and his angels will surround the city; but fire from God will consume them and cleanse the earth. The universe will thus be freed of sin and sinners forever. The 1,000 years begins with the general resurrection of the righteous and extends to the general resurrection of the wicked. During the 1,000 years, the righteous will live with Christ and reign in heaven, participating in the judgment of the wicked dead. Only Satan and his angels will be alive on earth during the millennium.
The millennium is a 1,000-year period when the righteous will reign with Christ in heaven. Revelation 20:4
Judging the wicked dead will be part of the work of reigning with Christ. Revelation 20:6; 1 Corinthians 6:2-3
The millennial period is between the two resurrections. Revelation 20:4-6
Satan will be confined to earth during it. Revelation 20:1-3, 7
The earth will be desolate. Revelation 20:1; Jeremiah 4:23-26 (compare with Genesis 1:2); Revelation 6:14-17, 16:17-21
fter the millennium Christ and the righteous will return to earth in the Holy City. The unrighteous will be resurrected at this time and Satan will lead them in an attack on the City. Finally all sin and sinners will be destroyed.
Christ and the righteous will descend with the Holy City. Revelation 21:1-5
The unrighteous will be resurrected. Revelation 20:5
They will join Satan in a war against the Holy City. Revelation 20:7-10
Satan's army will be defeated. Revelation 20:9
The executive phase of the judgment will occur. Revelation 20:10-15
Fire will cleanse the earth of all the results of sin. Once the fire has done its cleansing work, it will go out. 2 Peter 3:10-13; Malachi 4:1 D Satan and sin will be destroyed. Ezekiel 28:18-19
At the return of Christ, the decision as to who would constitute the redeemed and who the wicked had already been made. The judgment which was given unto the saints must therefore be a judgment of verification. God's righteousness and justice must forever be vindicated before the universe. During the thousand years, every case will be scrutinized - no lingering doubts may remain - one harmonious chord must exist in heaven and with one voice all will proclaim:
...Great and marvellous are thy works, Lord God Almighty; just and true are thy ways, thou King of saints. Revelation 15:3
God's judgment will be declared righteous. (Romans 2:5; 2 Thess. 1:5; Genesis 18:25; Psalm 19:9)
In this millennial judgment, God's dealing with the rejectors of His truth and of evil angels will be scrutinized (Hebrews 10:26,27; 2 Peter 2:4,9; Jude 6). The saints will judge the world.
Do you not know that the saints will judge the world? And if the world will be judged by you, are you unworthy to judge the smallest matters? Do you not know that we shall judge angels? How much more, things that pertain to this life? 1 Corinthians 6:2,3 NKJV
After the thousand years and the verification of judgment in heaven, the final events in the great controversy between good and evil will take place. In this final drama, God s name will be fully vindicated. Every knee will bow, and evil will forever be eradicated. These events are described in Revelation chapters 20-22. As the book of Revelation is written in chiastic structure, with the heart of the chiasm (events dealing with the final events before the return of Christ) in the middle of the book, the events described in these chapters appear to be described in reverse sequence. (eg. the wicked surround the New Jerusalem in Revelation 20:9, but the city only comes down from heaven in Revelation 21:2). If the chiastic structure is taken into account, then the sequence of events can be readily discerned.
After the thousand years, Christ returns to the earth to execute final judgment on the rejecters of His truth, and to take back that which is rightfully His. It is then that the kingdom will be restored to the saints.
The prophet Zechariah describes the coming of the Lord with all His saints, and how the feet of the Lord touch the earth to create a great plain (something that did not happen at the Second Coming. See Zechariah 14:4-5) The ancient prophecies made to literal Israel could have had their fulfilment in Israel of old if they had been obedient to God. The old covenant promises were transferred to spiritual Israel when they rejected the Messiah. The essence of the prophecy in Zechariah thus still applies and reaches its final fulfilment in the return of Christ after the millennium.
The New Jerusalem then descends from heaven...
And I, John, saw the holy city, New Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband. Revelation 21:2
From the safety of the city, the redeemed will then witness the final events which will end the great controversy between Christ and Satan. Satan will have had a thousand years to reflect upon the consequences of his actions and the sentence that awaits him.
Now when the thousand years have expired, Satan will be released from his prison and will go out to deceive the nations which are in the four corners of the earth, Gog and Magog, to gather them together to battle, whose number is as the sand of the sea. Revelation 20:7,8 NKJV
Satan had been bound when the wicked were slain at the first coming of Christ. The wicked that died would not come to life until a thousand years had expired.
But the rest of the dead lived not again until the thousand years were finished... Revelation 20:5
The resurrection of the wicked of all ages looses the chains of circumstances which had bound Satan, and he spurns the resurrected millions on to take the Holy City in one final effort to retain power.
...and will go out to deceive the nations which are in the four corners of the earth, Gog and Magog, to gather them together to battle, whose number is as the sand of the sea. Revelation 20:8 NKJV
In Ezekial 38:2 and 39:6, Gog, the king of Magog is described as an enemy of God's people. He is described as the leader of the host that would attack restored Israel. (Ezekial 38:2, 14, 16-19) but he would meet his end. This would happen "after many days" (Ezekial 38:8)
And it will come to pass at the same time, when Gog comes against the land of Israel,' says the Lord God, 'that My fury will show in My face. For in My jealousy and in the fire of My wrath I have spoken: "Surely in that day there shall be a great earthquake in the land of Israel..."' Ezekial 38:18,19 NKJV
God destroys Gog and Israel does not battle at all. No historic figure has as yet been identified with Gog, and he stands as a symbol of the leader of rebellion, Satan himself.
God permits this final act of rebellion by Satan and his hosts together with the resurrected wicked to dispel any lingering doubt as to the antipathy of those arraigned against God and His people. Good and evil stand opposite each other. The saints within the city, the wicked without.
Then I saw a great white throne and Him who sat on it, from whose face the earth and the heaven fled away. And there was found no place for them. And I saw the dead, small and great, standing before God, and books were opened. And another book was opened, which is the Book of Life. And the dead were judged according to their works, by the things which were written in the books. The sea gave up the dead who were in it, and Death and Hades delivered up the dead who were in them. And they were judged, each one according to his works. Then Death and Hades were cast into the lake of fire. This is the second death. And anyone not found written in the Book of Life was cast into the lake of fire. Revelation 20:11-15 NKJV
Satan and the wicked will be destroyed by fire.
...and fire came down from God out of heaven and devoured them. The devil, that deceived them, was cast into the lake of fire and brimstone... Revelation 20:9,10
Then he will also say to those on the left hand, 'Depart from Me, you cursed, into the everlasting fire prepared for the devil and his angels...' Matthew 25:41 NKJV
With this final destruction of Satan, the great controversy ends. Satan and his host (Gog and Magog) are destroyed by fire.
The fire that destroys the wicked also cleanses the earth.
But the day of the Lord will come as a thief in the night, in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat; the earth also and the works that are in it shall be burned up. Seeing then that all these things shall be dissolved, what manner of persons ought you to be in all holy conversation and godliness, looking for and hastening the coming of the day of God, wherein the heavens being on fire shall be dissolved, and the elements will melt with fervent heat? Nevertheless we, according to His promise, look for new heavens and a new earth wherein dwelleth righteousness. 2 Peter 3:10-13
God restores the earth to its original beauty - the earth is made new.
Now I saw a new heaven and a new earth, for the first heaven and the first earth were passed away. And there was no more sea. Revelation 21:1..."http://amazingdiscoveries.org/websto...ted-millennium