1 Thessalonians 4:16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
17 Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
18 Wherefore comfort one another with these words.
This is the prophecy of the rapture event. The words "caught up" (harpazo in Greek) is "raptus" in Latin, from which the English word "rapture" is derived.
(I point this, because some have been known to say that the word "rapture" is not present in the Bible!)
This is the same event typified in Revelation 4:1-2 when the Lord utters the words "Come up here!" in a voice loud as a trumpet.
It reminds us of the time when of the time when Jesus called forth Lazarus from the dead:
John 11:43 And when he thus had spoken, he cried with a loud voice, Lazarus, come forth.
When Jesus called "Lazarus, come forth" only Lazarus rose from the dead.
In the day of the Rapture, Jesus will just shout "Come" and all of us will come forth. He just has to say, "Come up here!" and we will all be up there at the midway point in the sky, to meet the Lord in the air.
The comparison with the resurrection of Lazarus is appropriate, because "the dead in Christ shall rise first." Then the living will be caught up (raptured).
Clearly the dead (whose spirits are already in heaven) will find their bodies have just been raised at the shout of the Lord, the voice of the archangel and the shofar of God. Their bodies, corrupted in the grave, will put on incorruption. And they will come with Christ to the meeting point in the sky.
Then those living at that time will find their mortal bodies have put on immortality, as they are caught up, to meet Christ and the resurrected saints at the appointed meeting place.