What does 2 Thessalonians 2:6 mean?

This verse continues Paul's statement in verse 5 about the Thessalonians' prior knowledge. This was in regards to the man of lawlessness: the false prophet of Revelation 13:11–18. Paul writes that these Christians know what is holding back the lawless one's evil from coming to full fruition. In the following verse Paul expands on what or who is holding back the man of lawlessness from performing his evil deeds to the fullest extent.

Without a doubt, evil is raging today. It manifests itself in heinous crimes, profane and blasphemous speech, sexual immorality, secularism, greed, hatred, and a growing disdain for God. And yet, wicked conditions will reach an unparalleled level when the man of lawlessness is revealed. He will personify evil and will lead an unprecedented rebellion against God. As in the days of Noah, the human condition even now grieves God and invites His judgment (Genesis 6:5–6), But, just as God witnessed to that generation through Noah (2 Peter 2:5), He confronts and restrains evil today through His witnesses.

Verses 6 and 7 also serve to remind us about the relationship between God and human suffering. When human beings wonder why God "does nothing" to stop evil, this passage should come to mind. As bad as it might seem, at times, the fact is that God is "restraining" evil from being even worse.