Some people think Revelation 7:14 means there will be survivors who endure to the end of the Great Tribulation and come out of it on the other side of it in time.
But I believe it means Babylon the Great being the cause of the tribulation and it is warned to "get out of" Babylon the Great so you do not share in her sins, coming out of her. Revelation 7:14 pictures the people who are obeying the order to get out of Babylon the Great. The great crowd stands in opposition to Babylon the Great. It is viewed spiritually and spans centuries. The crowd is always present but there are now very few left. But that is just one person's opinion.
But I believe it means Babylon the Great being the cause of the tribulation and it is warned to "get out of" Babylon the Great so you do not share in her sins, coming out of her. Revelation 7:14 pictures the people who are obeying the order to get out of Babylon the Great. The great crowd stands in opposition to Babylon the Great. It is viewed spiritually and spans centuries. The crowd is always present but there are now very few left. But that is just one person's opinion.