The term Yoga has been defined in various ways in the many different Indian philosophical and religious traditions.
It is a group of physical, mental, and spiritual practices or disciplines which originated in ancient India. It is one of the six Āstika (orthodox) schools of Hindu philosophical traditions.
The practice of yoga has been thought to date back to pre-Vedic Indian traditions; possibly in the Indus valley civilization around 3000 BCE. It is mentioned in the Rigveda and also referenced in the Upanishads. Although, it is most likely developed as a systematic study around the 5th and 6th centuries BCE, in ancient India’s ascetic and śramaṇa movements. The chronology of earliest texts describing yoga-practices is unclear, varyingly credited to the Upanishads. The Yoga Sutras of Patanjali date from the 2nd century BCE, and gained prominence in the west in the 20th century after being first introduced by Swami Vivekananda. Hatha yoga texts began to emerge sometime between the 9th and 11th century with origins in tantra.
The gurus from India later introduced yoga to the West, following the success of Swami Vivekananda in the late 19th and early 20th century with his adaptation of yoga tradition, excluding asanas. Outside India, it has developed into a posture-based physical fitness, stress-relief and relaxation technique. Yoga in Indian traditions, however, is more than physical exercise; it has a meditative and spiritual core. One of the six major orthodox schools of Hinduism is also called Yoga, which has its own epistemology, ontology and metaphysics, and is closely related to Hindu Samkhya philosophy.