In this chapter Lord Kṛṣṇa answers these different questions of Arjuna beginning with, "What is Brahman?" The Lord also explains karma, fruitive activities, devotional service and yoga principles, and devotional service in its pure form. The Śrīmad-Bhāgavatam explains that the Supreme Absolute Truth is known as Brahman, Paramātmā, and Bhagavān. In addition, the living entity, individual soul, is also called Brahman. Arjuna also inquires about ātmā, which refers to body, soul and mind. According to the Vedic dictionary, ātmā refers to the mind, soul, body and senses also.
Arjuna has addressed the Supreme Lord as Puruṣottama, Supreme Person, which means that he was putting these questions not simply to a friend but to the Supreme Person, knowing Him to be the supreme authority able to give definitive answers.