Krishna explains the seven terms - Brahman, Adhyatma, Karma, Adhibhuta, Adhidaivata, Adhiyajna, Prayana kala smarana to Arjuna.
He explains how one must depart one's body during death and what his last thoughts must be as they determine one's rebirth. This chapter is a deviant from other chapters which glorify jivanmukti (liberation when alive). This chapter talks about krama mukti, which is liberation in steps as a possibility after departing right.
Krishna talks about samsara chakra and how the embodied goes around for eons in samsara helplessly bound by their actions and declares that the only way to break the cycle is through liberation.