The Yoga Sutras of Patanjali are 196 Indian sutras (aphorisms) that constitute the foundational text of Raja Yoga. Yoga is one of the six orthodox astika schools of Hindu philosophy, which, according to the Yogatattva Upanishad, is divided into four forms - Mantrayoga, Layayoga, Hathayoga and Rajayoga - the last of which is the highest (or royal) practice.
Although the Yoga Sutras have become the most important text of Yoga, the opinion of most scholars is that Patanjali was not the creator of Yoga, which existed well before him, but merely a great expounder.
In the Yoga Sutras, Patanjali prescribes adherence to eight "limbs" or steps (the sum of which constitute "Ashtanga Yoga", the title of the second chapter) to quiet one's mind and achieve kaivalya. The Yoga Sutras form the theoretical and philosophical basis of Raja Yoga, and are considered to be the most organized and complete definition of that discipline. The Sutras not only provide yoga with a thorough and consistent philosophical basis, they also clarify many important esoteric concepts which are common to all traditions of Indian thought, such as karma.