From Wikipedia on 22-Sep-2014
Hatha yoga (Sanskrit: हठयोग haṭhayoga, About this sound listen (help·info) IPA: [ɦəʈʰəˈjoːɡə]), also called haṭhavidya (हठविद्या), is a kind of yoga. The word haṭha (lit. ‘force, violence’) denotes a system of physical techniques supplementary to a broad conception of yoga.
As a part of Hindu origin, Hindu tradition believes that Shiva Himself is the founder of hatha yoga.
In the 20th century, hatha yoga, particularly asanas (the physical postures), became popular throughout the world as physical exercises, and is now colloquially termed “yoga”.
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Many modern schools of hatha yoga in the West derive from the school of Tirumalai Krishnamacharya, who taught from 1924 until his death in 1989. Among his students prominent in popularizing yoga in the West were K. Pattabhi Jois famous for popularizing the vigorous Ashtanga Vinyasa Yoga style, B. K. S. Iyengar who emphasized alignment and the use of props, Indra Devi and Krishnamacharya’s son T. K. V. Desikachar.
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Yoga’s combined focus on mindfulness, breathing and physical movements brings health benefits with regular participation. Yoga participants report better sleep, increased energy levels and muscle tone, relief from muscle pain and stiffness, improved circulation and overall better general health. The breathing aspect of yoga can benefit heart rate and blood pressure.