Bottom line: Tribulation proves the profession or rejection of faith in Christ.
The Tribulation will be the worst time in human history and the worst time in Israel's history. It will be a time of judgment poured out on an unbelieving world, a time of refinement for the nation of Israel, and a time to of disestablishment for Satan's reign as god of this world. God will pour out His judgment through a series of plagues known as the Seal, Trumpet,and Bowl judgments, each series intensifying in severity.
In light of the coming judgments of tribulation, how can we respond today? We can preach the gospel to the ends of the world. We can pray for God's rule in heaven to abide on this earth. We can praise the Lamb of God for His salvation. We can prove our profession of faith in Christ as we trust Jesus no matter the hardships and difficulties to come.