The word Rapture comes from the Latin word, rapio, which means to seize or snatch, is the equivalent of the Greek word harpazo used in the 1 Thessalonians 4:17, which means "caught up."
There are several schools of thought on when the Rapture will occur...Mostly Pre, Mid, or Post Tribulation. I believe it is Pre-Trib, not because that is my preference, but based on scripture. Revelation is a chronological order of events. In the first three books of Revelation Jesus is speaking to the Church. From Chapter 4 onward the Church is not mentioned again (because they have been removed) Revelation 3:10 Since you have kept my command to endure patiently, I will also keep you from the hour of trial that is going to come on the whole world to test the inhabitants of the earth.
Revelation 3:22 Whoever has ears, let them hear what the Spirit says to the churches.”
The Rapture is the next prophetic event on the prophetic calendar. All other prophesies that must occur before the rapture have already been fulfilled.
2 Peter 2:9 The Lord knows how to rescue the godly from trials, and to keep the unrighteous under punishment until the day of judgment.
Thessalonian 5:9 For God did not appoint us to suffer wrath but to receive salvation through our Lord Jesus Christ.
I Corinthians 15: 51-52 Behold, I shew 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 trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
Luke 17:34-36 I tell you, in that night there will be two in one bed. One will be taken and the other left. There will be two women grinding together. One will be taken and the other left.
Matthew 24:31
And he will send out his angels with a loud trumpet call, and they will gather his elect from the four winds, from one end of heaven to the other.
The Rapture is not to be confused with the Second Coming of Jesus, where he comes in the clouds (with his Raptured Church) and every eye shall see him...that is a separate event which happens after the Tribulation. Revelation 17:14 They will wage war against the Lamb, but the Lamb will triumph over them because he is Lord of lords and King of kings-and "with him will be his called, chosen and faithful followers."
Matthew 24:42 Therefore, stay awake, for you do not know on what day your Lord is coming.
*The last "trump" refers to the 100 trumpets during the Feast of Trumpets (or Rosh HaShanah). The last trump, number 100, is called The Tekiah Gedolah, which means "the last trump," a very long final note, which symbolizes the hope of redemption.