Source :HITXP Articles by Gurudev(I read this article and wanted to share in my blog with all of you :-) really interesting one)
The Hindu Gotra System – Male Lineage Identification
The Gotra is a system which associates a person with his most ancient or root ancestor in an unbroken male lineage. For instance if a person says that he belongs to the Bharadwaja Gotra then it means that he traces back his male ancestry to the ancient Rishi (Saint or Seer) Bharadwaja. So Gotra refers to the Root Person in a person’s male lineage.