The event prophesied in 1 Thessalonians 4:16-18 and 1 Corinthians 15:51-52, where Christ comes down in the clouds and the dead believers that are in heaven are resurrected with their new, glorified bodies and caught up to Jesus in the clouds, and then those true believers with faith alone in the gospel (1 Corinthians 15:1-4) that are alive on earth, their bodies are transformed into their new, glorified bodies and then are caught up together with Jesus in the clouds, and then Jesus takes us all to heaven for 7 years while the Tribulation is happening on the earth.
Hundreds of millions of people will suddenly vanish. A strong delusion will come over the whole world to explain away the rapture, and it will probably be an alien abduction.
Young children and babies that can’t comprehend the gospel yet may even be taken as well.
1 Thessalonians 4:15-17 — For this we say to you by the word of the Lord, that we who are alive and remain until the coming of the Lord will by no means precede those who are asleep. For the Lord Himself will descend from heaven with a shout, with the voice of an archangel, and with the trumpet of God. And the dead in Christ will rise first. Then we who are alive and remain shall be caught up together with them in the clouds to meet the Lord in the air. And thus we shall always be with the Lord.
1 Corinthians 15:51-52 — Behold, I tell you a mystery: We shall not all sleep, but we shall all be changed— in a moment, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, and the dead will be raised incorruptible, and we shall be changed.