The Revelation tells us who they are and here is the key to understanding it,
Write the things which thou hast seen, and the things which are, and the things which shall be hereafter; Rev 1:19
What did John see? Jesus Christ glorified, chapter 1
What are the things which are? The Church, chapters 2 & 3
What are the things to come? Come after what, the Church, starting with chapt 4:1 through the rest of the book, it's all layed out chronologically.
What does Chapt 4:1 say,
After this I looked, and, behold, a door was opened in heaven: and the first voice which I heard was as it were of a trumpet talking with me; which said, Come up hither, and I will shew thee things which must be hereafter. Rev 4:1
After this, John was the itinerant pastor to the seven churches, they were located on a Roman postal route, just look at the map in the back of your Bible, the seven churches named are in a circle, hence after the Church, where did the Voice (Jesus in the first chapter) say to him (symbolic or representing the church) come up here! Where is up here? After the Bride (Church) is with Jesus we are told what is going to happen on planet earth, Chapt 6-19 the Tribulation, so you answer your own question, who will be the saints that come out of the Trib, here is a hint for you, where will they be and what will they do for all of Eternity, Rev 7:14, 15
Blessing,
Gene