The 144,000 refers to 12,000 people from each of the twelve tribes of Isreal. 12,000 times 12 equals 144,000.

The bible says in the book of Revelations in the last days, (the days before the return of Christ) a plague will be set forth unto to the earth the most horrible that people have ever seen. In that time people will be asked to take the mark of the beast. Of Those who don't, their lives will be tortured by the majority who do and they will eventually be killed but reedeemed by GOD who will accept them into the kingdom of heaven for following his ways, no matter the circumstances.

The 144,000 will be spared the tourtue, famine and other plagues of the time because they will be taken like thieves in the night to the kingdom of heaven to live with their heavenly father. These people are considered to be "saved" "Saved" people try to life their lives following the commandents of God and have accepted Jesus as their savior.

Now depending on your faith fill in Jesus and God for your most high, but same story applies. With my father being a pastor, (yes I am a PK) I heard this story many times.