It consists of 195 aphorisms, divided into four sections. It describes principles of yoga practice, results and freedom obtainable through yoga.
Many English translations exist.
It is part of a long poem called the Mahabharata, which is a treatise on yoga. The Bhagavad-Gita is a story of a discussion between Prince Arjuna and the god Krishna over a battle that Arjuna is duty bound to fight. Arjuna is reluctant to fight because he is afraid, abhors violence and it involves fighting his family. Krishna shows him that he has a sacred duty to fight for what is correct and that the outcome is not to be considered. All of these texts come in many English translations.