There are many Christians who believe that the second coming of Jesus Christ will be in two phases. First He will come for believers, both living and dead, in the "rapture"; read 1 Thessalonians 4:13-17. In this view, the rapture—which is the transformation and catching up of all Christians, dead or alive, to meet Christ in the air—will be secret, for it will be unknown to the world of unbelievers at the time of its happening.
The effect of this removal, in the absence of multitudes of people, will, of course, be evident on earth. Then, second, after a period of seven years of tribulation on earth, Christ will return to the earth with His church, the saints who were raptured (Matthew 24:30, 2 Thessalonians 1:7, 1 Peter 1:13, Revelation 1:7). He will be victorious over His enemies and will reign on the earth for a thousand years (the millennium) with His saints, the church.
After the thousand years, living unbelievers and the wicked dead now raised to life will be judged at the great white throne judgment. They will then be cast into the lake of fire, while the saved will live forever with Christ in a new heaven and earth (Revelation, chapters 19-22).
Many other evangelical Christians believe that Christ's return and the rapture will not occur until the seven years of the tribulation have ended. As far as the latter view is concerned, the rapture will not be secret, since it will be part of Christ's visible and triumphant return to end this present evil age (1 Thessalonians 4:13-17). At this point, interpreters differ as to whether there will be a literal thousand year reign of Christ on earth or whether the white throne judgment and the new heaven and earth will immediately appear.
All Christians do not agree on every detail of what will occur in the final events of this world's history. Some of these events and their order of occurrence have simply not been made clear in the Bible. What is important is that all Christians hold in common that Christ will ultimately return bodily, visibly, and gloriously to reign and rule with His resurrected and transformed saints forever and ever. The details of this great event will be made known in God's own time.