The Bhagavad Gita is one of the fundamental texts of Hinduism, and documents the conversation between Krishna and Arjuna as Arjuna prepares to go into battle against the Kauravas for battle of the kingdom of Hastinapura.
The Gita is written in Sanskrit and has been translated into virtually every language. It is dated sometime between 1000 and 700 B.C.E., close to when recorded history began in India, and when the battle that became the Mahabarata supposedly occurred.
The Vedas, dated earlier (around 1500 B.C.), are considered the most fundamental texts of Hinduism, but the Gita has become a stand-alone text that scholars and devotees return to for its emphasis on self-mastery. Krishna is the sole deity who speaks in the Gita, unlike other Hindu texts which outline a proliferation of divinities. He ascribes himself full omnipotence as well, but most scholars see the Gita fitting in with the tradition of other Hindu texts, where every God assumes the powers of other Gods in order to illustrate the true potency of divinity.
The Gita is now considered as seminal a text as the Koran, the Bible, and other bases of major religions. But the Gita is seen as less a religious than a philosophical text, outlining a way of life.