Regarding the question of the millennium (the 1000 years of Revelation 20), the return of Christ will take place either before His millennial kingdom (pre-mill) or after (post-mill).
There are two types of pre-mills: historic pre-mill and dispensational pre-mill, but they both agree that Christ will return before the millennium is established.
According to historic pre-mills, Christ will return to rapture His Church at the end of a world-wide tribulation, to resurrect the deceased saints, and to conduct the judgment of the righteous. Christ will then descend to earth with His glorified saints, fight the battle of Armageddon, bind Satan, and establish a world-wide political kingdom, in which Christ will reign from Jerusalem for a thousand years. At the end of the millennium, Satan will be loosed, and a massive rebellion against Christ’s kingdom will occur. Finally, God will intervene with fiery judgement to rescue Jesus and the saints, which will be followed by the resurrection and judgment of the wicked.
According to dispensational pre-mills, Christ will return to rapture His Church, meeting her in the air, before the seven-year tribulation. After this, the Lord will return to the earth (His Second Coming) to establish His kingdom on the earth for a thousand years, during which time all the promises given to Israel in the OT will be fulfilled (including a literal rebuilding of the temple).
Both post-mills and a-mills agree that Christ will return to rapture His Church after the millennium. They both agree that Christ’s kingdom was inaugurated when He ascended into heaven and sat down at God’s right hand. Post-mills teach that the gospel will gradually permeate the entire world, and eventually usher in a golden age (perhaps literally 1000 years) of rich spiritual blessings, which will be followed by Satan’s little season of brief apostasy, a final tribulation and conflict with the forces of evil, and thereafter by the simultaneous occurrence of Christ’s return, the general resurrection, and the final judgment.
Amillennialism [no literal 1000 years]
A-mills hold that since Christ’s present reign at God’s right hand is the millennial kingdom, the number 1000 is not meant to be taken literally. Therefore, there will be no future “golden age” before Christ returns.
[Adapted from R.C. Sproul, Everyone’s a Theologian]