Jacob's 12 sons, in order of birth, from first to last, are: Reuben, Simeon, Levi, Judah, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, Joseph and Benjamin. Each one of the son's descendants form a family tree. The families descended from each son, based on the lineage of the father, is referred to as a "tribe." Jacob, whose name was changed to Israel, is the patriarch of all the children descended from each son, or tribe. The 12 lineages constitute the "Twelve Tribes of Israel."
Not all of Jacob's children were born from the same mother. Four women gave birth Jacob's sons. Rachael was Jacob's favored wife, though custom and an agreement with Rachael's father resulted in a marriage to Rachael's older sister, Leah, before Jacob and Rachel were wedded. Leah gave birth to Reuben, Simeon, Levi, Judah, Issachar and Zebulun. The second mother, Bilhah, was Rachael's servant and mother to Dan and Naphtali. Zilpah, Leah's servant, was mother to Gad and Asher. Rachael, in her old age, gave birth to Joseph and Benjamin.
Joseph was highly favored by Jacob, as the first born son of his favorite wife. Jealousy from the older brothers resulted in Joseph being sold into slavery and the faking of his death to Jacob. Joseph later worked in the Egyptian Pharaoh's court, and correctly interpreted the Pharaoh's dream, earning him a place of honor. During a seven-year famine, Jacob's brothers came to Egypt to buy grain. Joseph recognized them and became reunited with the family bringing together all the "tribes of Israel" into Egypt. Over time the children of Israel, or "Israelites" became menial workers and slaves to the Egyptians until they were led out by Moses.
Each tribe of Israel was granted a portion of land in the area now known as Israel. The tribe of Levi is excluded from the settlements, as they were holders of the priesthood and served the other 11 tribes. The tribe of Joseph received a double portion of allotments, split between his sons Manasseh and Ephraim. While Ephraim and Manasseh are considered tribes, they together constitute the tribe of Joseph, one of the "Twelve Tribes of Israel."