The Rapture will happen before the Tribulation. Jesus will take his bride, which are those who believed on what He did alone at the cross to save them. You might ask, "What did Jesus do alone at the cross to save us?"

Corinthians 15:1-4 MOREOVER BRETHREN, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;

(2)By which also ye are saved, if ye keep in memory what I preached unto you, unless ye believed in vain.

(3)For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;

(4) And that he was buried, and that he rose again the third day according to the scriptures:

There is a parable in Matthew 13 about tares and wheat. Which is about gathering the nations together before throwing it to be burned. And the rapture happening before the gathered nations were to be burned.

Mathew 13:24-26 Another parable put he forth unto them, saying, The kingdom of heaven is likened unto a man which sowed good seed in his field:

(25) But while men slept, his enemy came and sowed tares among the wheat, and went his way.

(26)But when the blade was sprung up, and brought forth fruit, then appeared the tares also.

The man is the Lord. The world is the field. The seed is the word of God. The wheat are the Christians. The tares are false Christians (tares look similar to wheats)/nations. And the enemy is satan.

Matthew 13:27-30 So the servants of the householder came and said unto him, Sir, didst not thou sow good seed in thy field? from whence then hath it tares?

(28)He said unto them, an enemy hath done this. The servants said unto him, Wilt thou then that we go and gather them up?

(29)But he said, Nay; lest while ye gather up tares, ye root up also the wheat with them.

(30)Let both grow together until the harvest: and in the time of harvest I will say to the reapers, Gather ye together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.

The tares (nations and false Christians) will be bundled (gathered) to be burnt, while the wheat (Christians) will the gathered (raptured) to the barn(heaven). Notice how the tares are only to be gathered/bundled and not yet to be burnt while the wheat is still there. It is only after the church have been raptured will the tribulation start.

Zephaniah 3:8 Therefore wait ye upon me, saith the LORD, until the day that I rise up to the prey: for my determination is to gather the nations, that I may assemble the kingdoms, to pour upon them mine indignation, even all my fierce anger: for all the earth shall be devoured with the fire of my jealousy.

Romans 8:23 And not only they, but ourselves also, which have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, to wit, the redemption of our body.

Philippians 3:20-21 For our conversation is in heaven; from whence also we look for the Saviour, the Lord Jesus Christ: (21)Who shall change our vile body, that it may be fashioned like unto his glorious body, according to the working whereby he is able even to subdue all things unto himself.

When we believe on the finished work of the Lord Jesus Christ at the cross, we are saved, that is, our soul. As for our bodies, to those who have passed and to those who are still alive on earth, all those in Christ, are, as Romans 8:23 mentions, waiting for the redemption of our body. Which is the rapture.

1 Corinthians 15:51-54 Behold, I show you a mystery; We shall not all sleep, but we shall all be changed,

When Paul mentions mystery, it means that it's something that hasn't been reveal before Paul, . "...We shall not all sleep..." are all those in the body of Christ, both those who have passed and those who are still alive.

1 Corinthians 15:52 In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.

So the rapture will happen in a moment, in the twinkling of an eye. Both those who are dead and alive will be raptured. "...we shall be changed."

1 Corinthians 15:53 For this corruptible must put on incorruption, and this mortal must put on immortality. (54)So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.

The corruptible is the fleshly body our soul is residing in. The tent, the vessel. Although we are made a new creature and sealed with the Holy Spirit after putting our faith on the gospel of Jesus Christ (born again), a soul with no sin (since our soul is now washed with the blood of Jesus Christ), our mortal earthly body is still corrupt. Our mortal body hasn't been redeemed yet, until the rapture happens.

Which is why the corruptible (sinful flesh) must put on incorruption (a new body) and the mortal must put on immortality.

Romans 8:9 Much more then, being now justified by his blood, we shall be saved from wrath through him. (10)For if, when we were enemies, we were reconciled to God by the death of his Son, much more, being reconciled, we shall be saved by his life

As mentioned in Romans 8:9, those who are justified by his blood (Jesus), notice how we are saved from the wrath through Jesus. So those in the body of Christ will not go through the wrath (tribulation). Why? Because Jesus took God's wrath in our place. Where? At the cross, where Jesus died for our sin, was buried and on the third day rose from the dead.

1 Corinthians 15:1-4 MOREOVER, BRETHREN, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; (2)By which also yet are saved, if ye keep in memory what I preached unto you, unless ye believed in vain. (3)For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; (4)And that he was buried, and that he rose again the third day according to the scriptures: