According to the Bible, who are the 144,000 and are they the only Christians who will go to heaven?

Update: In response to someone who has me blocked: The Kingdom Interlinear Translation of the Christian Greek Scriptures originally showed that Revelation 5:10 said the kingdom of priests who serve God "will reign ON the earth" yet the New World Translation now says they will reign OVER the earth.
Update 2: Just been reviewing all these answers and I'm picking up a thread there. There is no doubt the Bible says 144,000 will be joint rulers and priests with Christ Jesus during the millennial kingdom. But that's not the question! The question is WHO are they (where do they come from) and are they the ONLY ones... show more Just been reviewing all these answers and I'm picking up a thread there. There is no doubt the Bible says 144,000 will be joint rulers and priests with Christ Jesus during the millennial kingdom. But that's not the question! The question is WHO are they (where do they come from) and are they the ONLY ones who will go to heaven. Some people don't seem to want to address this specifically. Did Jesus ever say only 144,000 persons will go to heaven? If so, where did he say it?
Update 3: Oh, and I haven't given anybody a thumbs' down. All opinions welcome.
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