Yoga is a term that has two meanings. It is both (1) a school of thought in the Hindu religion and (2) a system of mental and physical exercise developed by that school. Followers of the yoga school, who are called yogis or yogins, use yoga exercise to achieve their goal of isolation of the soul from the body and mind. Many non-Hindus in Western countries practice some form of yoga exercise in hope of improving their health and achieving peace of mind. The word yoga means discipline in Sanskrit, the classical language of India.
According to the yoga school, every human being consists of prakrti and purusha. Prakrti includes a person's body, mind, and ego (conscious self). Purusha is pure, empty consciousness--the soul. The yoga school teaches that the soul is completely separate from the rest of a person, but that the person does not realize it. Human beings suffer because they wrongly believe that their soul is bound to their body and mind. The yoga school, through yoga exercise, aims to give people prajna (understanding) of the meaning of their soul. After a person has obtained this understanding, his or her soul will gain moksha (release) from the samsara (cycle of rebirth) in which Hindus believe.
A yogi, under the guidance of a guru (teacher), goes through eight stages of training on the way to moksha. The yogi learns: (1) disciplined behavior, called yama; (2) positive values (niyama); (3) bodily postures, such as the lotus position (asana); (4) control of breathing (pranayama); (5) control of the senses (pratyahara); (6) fixing of the mind on a chosen object (dharana); and (7) meditation (dhyana). The eighth stage, called samadhi, is a state of concentration in which yogis realize that their soul is pure and free, and empty of all content. A yogi who has completed these eight stages has reached kaivalya. Kaivalya is total isolation of the soul from the body, from all other souls, and from all of nature.
Various forms of yoga have become popular in the United States and Europe. Transcendental Meditation is a simplified version of the yoga of Hinduism. Bhakti-yoga involves the dedication of all actions and thoughts to a chosen god. Members of the Hare Krishna movement practice bhakti-yoga by dedicating themselves to the god Krishna. Hatha-yoga, which stresses difficult bodily postures and breathing techniques, has become popular as a method of gaining better health. People also study hatha-yoga for the unusual control some yogis develop over such functions as metabolism and blood flow.