In the biblical Book of Genesis, Cain and Abel are the first two sons of Adam and Eve. Cain, the firstborn, was a farmer, and his brother Abel was a shepherd. The brothers made sacrifices to God, but God favored Abel's sacrifice instead of Cain's. Cain then murdered Abel, whereupon God punished Cain by condemning him to a life of wandering. Cain then dwelt in the land of Nod (נוֹד, 'wandering'), where he built a city and fathered the line of descendants beginning with Enoch.

Academic theologian Joseph Blenkinsopp holds that Cain and Abel are symbolic rather than real. Like almost all of the persons, places and stories in the Primeval history (the first eleven chapters of Genesis), they are mentioned nowhere else in the Hebrew Bible, a fact that suggests that the History is a late composition attached to Genesis to serve as an introduction. Just how late is a matter for dispute: the history may be as late as the Hellenistic period (first decades of the 4th century BCE), but the high level of Babylonian myth behind its stories has led others to date it to the Babylonian exile (6th century BCE).

More Info: en.wikipedia.org