This passage refers to a time when Jesus calls to himself those who have believed in him. Scholars differ on whether or not this refers to Christ's final glorious return. (See: [[rc://en/tw/dict/bible/kt/believe]])
This is the same as "son of destruction" and "lawless one" in this chapter. Paul associates him with Satan actively working in the world. (See: [[rc://en/tw/dict/bible/kt/antichrist]])
Paul could be referring to the Jerusalem temple that the Romans destroyed several years after he wrote this letter. Or he could be referring to a future physical temple, or to the church as the spiritual temple of God. (See: [[rc://en/ta/man/translate/figs-explicit]])