The Mahabharata is a Sanskrit epic poem describing the conflict between two sets of cousins over an empire.
The central story of the Mahabharata is that of the warring cousins known as the Pandavas and the Kauravas. The five Pandava brothers are the story's protagonists and they come to share a common wife named Draupadi.
The conflict between the Pandavas and the Kauravas escalates throughout the story and culminates with the Battle of Kurukshetra. Before this battle, Arjuna (an archer who is the most skilled Pandava warrior) participates in a dialogue on spirituality with the Hindu god Krishna. This lesson is often separated from the Mahabharata and considered a work unto itself known as the Bhagavad Gita.
Prior the the Battle of Kurukshetra, Arjuna is told by his mother Kunti that one of the allies of the Kauravas (a great warrior named Karna) is her son also. Karna's father is the Hindu sun god Surya. Kunti pleads with Arjuna not to fight in the upcoming battle, as he and his brothers would be at war with their half-brother Karna. Arjuna eventually takes part in the battle and kills Karna.