If you prefer audio version, here is a link to a BBC lecture about Yoga. Here, I am stating the definition given by Yoga Alliance: "Yoga is a polythetic system of physical, mental, and spiritual practices and disciplines which originated in ancient India and South Asia. Throughout history, various groups in India, and in other cultures, geographies, and religious and secular contexts, have defined and redefined yoga according to the differing circumstances, passions, and goal

Yoga like practices are mentioned in the Rigveda (one of the oldest sacred texts) which dates back to early first millenium BCE. However systematic yoga concepts, particularly those associated with meditations and ascetic practices, began to take a shape between 5th-6th centuries BCE. The formalization of yoga into a structured system from Vedas and verbal knowledge, started with Patanjali's Yoga Sutras*(Patanjali a scientist from India), written around 325 CE. He introduced

Explanation of different types of yoga