Chapter 15 of the Bhagavad Gita, titled 'Purusottama Yoga', consists of 20 verses that outline the nature of the material world, the individual soul (jīva), and the Supreme God (Ishvara). It uses the metaphor of an upside-down banyan tree to illustrate worldly entanglement, emphasizing the need for detachment and surrender to achieve liberation. The chapter captures the essence of the Gita and Vedas, highlighting the oneness of individual souls and the Supreme Consciousness.