You can think of prana as "life force." In yoga, the word "prana" is used, but the same concept is present in many forms of philosophy, religion and medicine that arose in the Far East. In Chinese medicine, it's called "chi" or "qi." In some forms of Buddhism, it's translated as "energy wind" or "inner wind." Regardless of what it's called, moving, strengthening and cleansing our prana is one of the primary goals, if not the primary goal, of yoga, not to mention the goal of Tai Chi, Qigong, acupuncture, Reiki, certain forms of massage and certain meditative practices.