The Bhagavad Gita is a Hindu religious text which forms part of the longer epic poem the Mahabbarata. The text takes the form of a discussion between Krishna and Arjuna in which Krishna passes on his teachings. The conversation takes place before a battle in which Arjuna is to fight against some of his relatives.
Krishna is described in the text as the personification of the god of the universe and the Supreme Personality of God. Krishna says in the Bhagavad Gita that this knowledge was taught to him by the sun god. Krishna then passed it on to Manu, who passed it on to Iksvaku, who passed it on to his disciples. His teachings were lost over the centuries, meaning that Krishna has to explain them again to Arjuna.
There are five main topics in the book: the knowledge of God, Jivas, the living entities whose lives are controlled, Prakrti, material nature, time, the duration of the existence of the whole universe and Karma.