This document discusses breathing and the respiratory system in yoga. It explains that breathing involves inhaling oxygen and exhaling carbon dioxide. The main breathing organs are the nose, pharynx, larynx, trachea, lungs, and blood vessels. Proper breathing is important for physical and mental health, but most people breathe too shallowly. Practicing pranayama or breathing exercises can help improve breathing and provide benefits like increased lung capacity, blood purification, and mental calmness. The document also discusses the nadis, chakras, and different types of prana in the body.