Yoga is a healing system of theory and practice. It is a combination of breathing exercises, physical postures, and meditation that has been practiced for more than 5,000 years. 
While yoga evolved as a spiritual practice in Hinduism, in the Western world, a part of yoga, known as Asana, has grown popular as a form of purely physical exercise. Some Western forms have little or nothing to do with Hinduism or spirituality, but are simply a way of keeping fit and healthy.
Yoga was introduced to American society in the late 19th century by Swami Vivekananda, the founder of the Vedanta Society. He believed that India has an abundance of spiritual wealth and that yoga is a method that could help those who were bound by the materialism of capitalist societies to achieve spiritual well-being.
A survey released in May 2004 by the National Center for Complementary and Alternative Medicine focused on who used complementary and alternative medicine (CAM), what was used, and why it was used in the United States by adults age 18 years and over during 2002. According to this survey, Yoga was the 5th most commonly used CAM therapy (2.8%) in the United States during 2002.  Yoga is considered a mind-body intervention that is used to reduce the health effects of generalized stress.