The dispensation of the Millennium or the Millennial reign of Christ runs from the Second Advent of Christ to the end of human history and will last for 1,000 literal years. For these 1,000 years, the earth will have perfect environment. The human race (unbelievers) that survived the Tribulation and the Armageddon Campaign will be judged by our Lord Jesus Christ at His Second Advent. Here, Jesus Christ will separate all believers from unbelievers and remove the unbelievers from the earth. This is called the Baptism of the Fire and means that only believers (Jews and Gentiles) still alive on earth will enter the Millennium in their physical bodies. All other believers will be in resurrection bodies. The nation of Israel will be restored to the Land and God's unconditional covenants to Israel will be fulfilled. The remnant of Israel (believers) will begin the Millennium in the Land.
The Age of the Millennium is outlined in Revelation 20, Isaiah 11, Isaiah 35, Isaiah 64, Isaiah 65 and many other passages.
Since the believers that enter the Millennium will procreate, there will be a growing number of unbelievers that result. Even in perfect environment, some will still chose freely to reject the Gospel of Jesus Christ. Rev. 20:7-9.
“When the thousand years are completed, Satan will be released from his prison, and will come out to deceive the nations which are in the four corners of the earth, Gog and Magog, to gather them together for the war; the number of them is like the sand of the seashore. And they came up on the broad plain of the earth and surrounded the camp of the saints and the beloved city, and fire came down from heaven and devoured them.” (Revelation 20:7-9, NASB)
Life will be extended on earth. Capital punishment will be seldom used. Salvation, as for all dispensations, will be by faith alone in the work of the Lord Jesus Christ on the Cross. Old Testament sacrifices will be resumed.
At the end of the Millennium, Satan will be released and will institute his final revolt called the Gog and Magog Revolution. Jesus Christ will end this revolt just as suddenly and completely as He did the Armageddon Campaign 1,000 years earlier.
The universe will be destroyed followed by the Great White Throne Judgment or the Last Judgment. Following this last judgment by Jesus Christ Himself, Satan, all fallen angels, and all unbelievers will be cast into the Lake of Fire for eternity. Rev. 20:11-15.
“Then I saw a great white throne and Him who sat upon it, from whose presence earth and heaven fled away, and no place was found for them. And I saw the dead, the great and the small, standing before the throne, and books were opened; and another book was opened, which is the book of life; and the dead were judged from the things which were written in the books, according to their deeds. And the sea gave up the dead which were in it, and death and Hades gave up the dead which were in them; and they were judged, every one of them according to their deeds. Then death and Hades were thrown into the lake of fire. This is the second death, the lake of fire. And if anyone’s name was not found written in the book of life, he was thrown into the lake of fire.” (Revelation 20:11-15, NASB)