Yoga originated as one of the six orthodox schools of Indian philosophy and was systematized as a formal philosophy in the early centuries CE in Patañjali’s Yoga Sũtra. In practice, however, it dates back to 1 BCE and is believed to have been founded by Hiraṇyagarbha. 
According to Patañjali, yoga is a methodical effort to attain perfection, through the control of the different elements of human nature, physical and psychological.
Modern day yoga is based on the traditions of Hatha Yoga, which emerged as an offshoot of the yoga school of thought. This lays its main focus on āsana (posture) and prāṇāyāma (regulation of breath). Rāja Yoga focuses on dhyāna (fixed attention) and samādhi (concentration), the mental aspects of  yoga.
AtréYoga is comprised of 5 structured series of asanas developed by Zubin Atré.  These asana series are designed with variations on flexibility, strength, balance, and breath, based on in-depth awareness of human anatomy and movement.
Adjustments are the key element setting Atré Yoga apart from other yoga practices.  Teachers of the Atré Yoga method correct and refine your asanas so that you breathe more easily in various poses and get their maximum benefit.  Pranayam is also incorporated into the practice to help you explore the untouched corners of every asana you practice through an awareness of breath.
AtréYoga also approaches asanas with special attention to biomechanics.  By referring to anatomical detail, noting which muscles are activated and stretched, AtréYoga refines and adjusts asanas to make them more effective.  A complete cycle to which this approach has been devoted to and shared is the Biomechanics of the Sun Salutation.
The environment maintained in classes is one of positivity and encouragement.  To make sure each practitioner receives individual attention, Atré Yoga class sizes are kept small.  Sessions typically consist of up to eight students. Practitioners of different levels perform asanas at their own ability in the same class. With no levels and no competition, Atré Yoga is for everyone.