“Even a little study of the Bhagavad Gita,
like a drop of the flow of nectar,
is sufficient for enlightenment.”
— Shankaracharya, Bhaja Govindam 20
The Bhagavad Gita translates as The Song of God. It is a section of the Mahabharata which is itself the story of Krisna’s life. Krisna is an avatar of Vishnu, the sustainer, who is said to periodically send an avatar to restore light.
Ram was the avatar prior, spoken of in the Ramayana. The Yog Vasishta is the essence of the Ramayana in a similar way as the Gita. The 10th and final avatar for this cycle is to come, said to be riding a white horse, or more precisely, to be a white horse. (some prior avatars have been in animal forms)