Cooper explains the nature of the Great Tribulation in this two-part series. This event is a future event that will be associated with Antichrist’s persecution against the Church—contra preterism. And the Great Tribulation is not to be confused with the Day of the Lord’s wrath—contra pretribulationism.
For further explanation of the Great Tribulation, Charles Cooper provides an exegesis in his book, God’s Elect And The Great Tribulation: An Interpretation of Matthew 24:1-31 and Daniel 9. You can purchase it here.