It is my conviction, and that of the others who write for our Foundation, that the Rapture will occur before the Tribulation described in Revelation 6-19. The Rapture is only for the church, the body of Christ. It is described in 1 Thessalonians 4:13-18 and will include all living Christians and those believers who have died since the beginning of the Church Age (after Pentecost).
The 144,000 are not members of the church. They are Jews of the nation of Israel. The Tribulation (also called Daniel’s 70th week) continues God’s program for the nation of Israel. The church is a parenthetic period of an undetermined amount of time. The Rapture will finish God’s program for the church. After that, He will again begin to deal directly with the nation of Israel to complete his promises and program for them. The 144,000 are undoubtedly the first converts of the Tribulation and become the great evangelists of this period. Through them and other agents, many will come to Christ from every tongue, tribe, and nation (see Rev. 7).