The word "millennium" comes from two Latin words, mille, which means 1,000; annum, year. It means 1,000 years.
1M Rev. 20:5. This 1,000 years is bounded at each end, or marked off, by two great resurrections. The use of the word "first" in Rev. 20:5 proves that there will be two resurrections; for since there is a first, there must be a second resurrection.
2M John 5:28,29. Jesus taught there will be two resurrections--a resurrection of life, when the good will be raised, and a resurrection of damnation, when the evil or unrighteous people will be raised from the dead.
3M Rev. 20:6. Since all the righteous are raised in the first resurrection, it must be that all the wicked will be raised in the second resurrection.
4M Rev. 20:4. Since the righteous dead are brought from the dead to reign with Christ during the 1,000 years, that proves that these righteous ones are raised at the beginning of this 1,000 years.
The resurrection of the righteous takes place at the beginning of the 1,000 years. The resurrection of the wicked takes place at the end of the 1,000 years. Rev. 20:5. The millennium is this 1,000-year period between these two resurrections. As the righteous dead are raised at the second advent of Christ (1 Thess 4:16), this proves that it will be the coming of Christ at the last days to gather His saints that will mark the beginning of this 1,000-year period of Rev. 20. At Christ's second coming the righteous dead are raised, the living righteous are changed to immortality, and then all the righteous leave the earth to meet Jesus, and go with Him to the prepared mansions in heaven. 1 Thess 4:16,17; John 14:3.
5M Rev. 20:6. Hence the millennial reign of the saints with Christ is bound to be in the mansions of the New Jerusalem in heaven.
6M Jer. 25:30-33. The wicked who are alive on the earth at the appearing of Christ will be struck dead by His presence, and will lie here unburied on the earth. The wicked who may have died before Jesus comes will remain dead until the end of the 1,000 years. Rev. 20:5, first statement.
7M Isa. 24:1. Thus the earth will be made empty of all living human beings at the coming of the Lord.
8M Jer 4:23,27. The earth will be desolate without any living inhabitants during this 1,000 years.
9M Rev. 20:1-3. Satan will be bound on this earth during this 1,000 years, because all the righteous will be in heaven during this time, so that he cannot tempt them, while all the wicked will be dead, and he cannot deceive them.
All chance for sinners to be saved is forever closed at the beginning of this 1,000 years, when Jesus makes his second advent. Rev. 22:11,12. There is no such thing as any second opportunity for anybody during this 1,000 years. It is impossible for any of the wicked to hear the gospel during this time, because they are all dead. Rev. 20:5, first statement.
10M Rev. 21:2. At the close of the 1,000 years, the New Jerusalem will descend to the earth. This will be the time when the Lord will come with all His saints. Zech 14:4,5.
At the close of this 1,000 years the wicked will be raised, and this will loose the devil for a little season.
11M Rev. 20:7-9. This great army of resurrected wicked will attempt to capture the city of God which will then be resting on this earth on a prepared spot. They will surround this heavenly Jerusalem home of the saints to try to capture it. But God rains down on them coals of fire and brimstone. The earth itself will be melted into a lake of fire. (2 Pet. 3:10), the wicked will be destroyed everlastingly (Mal 4:1-3), and then God will reconstruct the earth into a perfect, sinless paradise, with the New Jerusalem for its capital and center.
12M Rev. 20:15; 21:1. The new earth follows the lake of fire. The righteous will reign forever in this new perfect earth under Christ as King of kings and Lord of lords.