People will be saved during the tribulation period. There will also be people who are martyred for their belief during this period. (Revelation 7) Many people from various racial and ethnic groups will be redeemed during the Tribulation, finding Christ as their Savior. One big difference between pre-Rapture and post-Rapture is that people will actually BELIEVE that the end of the world is at hand. That will come about because of all the different things that will happen on and to the earth during that time period.

Revelation is an interesting read. Confusing and frustrating at times, true, but a must-read for all Christians. I recommend a Bible with commentaries and footnotes from Schofield or Ryrie.