Prana is a force, the life force, the vital force and it is five sub forces. Each of them perform different physiological functions in this body. Shankaracharya uses an old Sankean principle to explain how we live or die. All compound things exist for the sake of something apart from them. The very experience of living which we have all of us right now isn't really due to prana but to consciousness.
Swami Sarvapriyananda teaches the Katha Upanishad, one of India's most revered texts which is also a part of the Vedas. It is a collection of philosophical poems representing a conversation between the sage Naciketas and Yama (god of death). They discuss the nature of Atman, Brahman and Moksha(liberation).