Yoga Philosophy

Yoga is a practical philosophy, not a religion, and requires no allegiance to any particular system of belief. It is a traditional Indian philosophy that involves the integration of the physical and spiritual in order to achieve a sense of well-being. In the practice of yoga, the body  is linked to the movement , mind and breath to bring about a feeling of balance, relaxation and harmony.
The practice of postures (Asanas) improves a variety of ailments, strengthens and tones muscles and develop flexibility. Various movements in the postures result in blood saturating, nourishing and cleaning the remotest parts of the body.
Psychologically, Yoga increases concentration,stills the mind and promotes a feeling of balance , tranquility and contentment.
The Indian Sages (Gurus) first developed the idea of Yoga to attain spiritual enlightenment  which required a systematic approach. They believed that by training physical body they could tame the mind, and there by improve the concentration and find their inner self or soul.
Hatha Yoga relates to the practice of special postures called ASANAS. These Asanas has evolved to work all parts of the body. They fall into families of postures, including forward bends, backward bends, standing poses, seated poses, twists, side-bending postures, balances, and inverted postures.
according to Patanjali's Sutras " Postures bring about stability of the body and poise of the mind". Practicing Asanas improves flexibility , vitality, and health, and activates the organs (heart, lungs, kidneys, liver, spleen, and pancreas). The true importance of postures is the connection between body and mind, so the two become interwoven, initiating the path from physical to spiritual awareness.
We have our own guide for the teaching of Yogasanas which may be useful not only to the teachers for whom it is meant, but also to others who may wish to learn how to practice some common Yogasanas. 
See some of the Yoga poses by Thomas Koovalloor, E-RYT 500 ( Registered with Yoga alliance) , age 60, started learning Yoga at the age of 7.