The Bhagavad-Gita is the holy Book Hindu religion, is presented here as a story that will be accessible to all world where Krishna and Arjun is the main part of Bhagavad-Gita. It begins in long-ago India when Arjuna Pandava is about to fight a war and asks Lord Krishna for aid and advice.
Lord Krishna (God) describes the working of spiritual world to Pandava: "When your service to Me never stops and is done only for My pleasure, and when you are friendly to every living being, I will lead you from this world of birth and death.
God has six qualities-- Aishwarya, Dharma, Gyana, Vairagya, Shree or Shreyas and Yashah . Here the Lord informs Arjuna about the system of yoga, "This yoga that I talked to you about is immortal". Fire will always burn. This is its nature and it has always been so. Similarly, the Karma yoga philosophy is also immortal and cannot be improved upon.
Bhagavad-Gita, was first spoken to the sun-god, After that he explained it to Manu, and Manu explained it to Ikshavaku, and in that way, by disciples succession, one speaker after another, this yoga system has been coming down.