Yoga is commonly known as a generic term for a physical, mental, and spiritual discipline
Yoga is commonly known as a generic term for a physical, mental, and spiritual discipline originating in ancient India and found in Hinduism, Buddhism, Jainism and Sikhism. Specifically, Yoga is one of the six orthodox schools in Hindu philosophy. It is based on the Yoga Sutras of Patanjali and aims to use meditation to attain spiritual insight and tranquility.
In the West, the term "yoga" is today typically associated with Hatha Yoga and its asanas (postures) or as a form of exercise, see Wikipedia on Yoga