Story goes as in Old Testament. Jacob had 12 sons named were Reuben, Simeon, Levi, Judah, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, Joseph, and Benjamin and one daughter called Dinah. These 12 sons became 12 Tribes. These are mentioned in the Bible 25 times. Now you have to decide that in Revelation 7 and 14 these 12 x 12000(in each tribe) = 144000 are these figures symbolic or ???
As described in Wikipedia. Check out yourself: https://en.wikipedia.org/wiki/Jacob