Upanishads are ancient Indian texts that delve into the nature of reality and the self, serving as foundational philosophical scriptures in yoga. These profound teachings explore metaphysical concepts such as the nature of existence, consciousness, and the relationship between the individual soul (Atman) and the universal consciousness (Brahman). The Upanishads emphasize spiritual knowledge and inner realization through contemplation and meditation, providing insights into the ultimate purpose of life and the paths to spiritual liberation (moksha).