The Puruṣottama Yoga is the fifteenth chapter of the Bhagavad Gita, which focuses on the qualities of the Supreme Being, Puruṣottama, and how one can attain liberation through devotion to Him. The chapter starts with Arjuna asking Krishna to explain the nature of the Supreme Being, as well as the difference between the material and spiritual worlds.
Krishna explains that the material world is temporary and full of suffering, while the spiritual world is eternal and full of bliss. He then goes on to describe the qualities of Puruṣottama, who is beyond the material world and the source of everything. He explains that one who understands the nature of Puruṣottama will attain liberation, and that devotion to Him is the highest form of spiritual practice.
Krishna goes on to describe the different types of devotees, including those who are motivated by material desires, those who are seeking knowledge, and those who are completely devoted to Puruṣottama. He explains that all types of devotees will eventually attain liberation, but those who are completely devoted to Puruṣottama will attain it quickly and easily.
The chapter concludes with Krishna urging Arjuna to surrender to Puruṣottama and to engage in devotional service to Him. He assures Arjuna that by doing so, he will attain the highest perfection of spiritual life.