We should expect a purging or refining of this material world, not an annihilation of it.
Tribulation may refer to the Great Tribulation occuring prior to the return of Christ. The Antichrist is satanically inspired and sets himself up as God.
The exact timing and nature of what is meant by the Millennium is debated between three viewpoints: Amillennialism, Postmillennialism, and Premillennialism.
This age is the time between the ascension of Christ and his return in glory.
In this Read the Bible video, Russell Moore explains the wedding picture of Revelation 21 and how we will one day feel “at home” in the cosmos.