Yoga is a five thousand year old tradition by which one may find inner peace.
To understand what hatha yoga is about it is helpful to know that in Sanskrit, the word yoga means to yoke or join together. Also, "ha" is sun and "tha" is moon. These two heavenly bodies represent the dualities which may be joined through the practice.
Hatha Yoga is a physical practice by which we may find balance. Through it we may learn to acknowledge and control opposing forces. The forces may be physical, psychological, and emotional. Balance may involve effort and ease, calm and chaos, mind and body. Ultimately the practice of yoga will lead to a union of the body, mind and soul.
Those who practice yoga asanas (postures) improve muscle tone, flexibility, strength, and stamina reduce body fat improve circulation and stimulate immunity reduce stress and tension improve concentration and increase creativity boost self esteem and develop compassion.
The physical practice of asana is but one aspect of yoga. Asana in fact serves to prepare the body for the insight of meditation. Altogether, there are eight aspects to the practice. They are often called the eight limbs of yoga. The 196 Yoga Sutras (threads) of the master Patanjali describe all aspects of the practice. They provide instruction on how to lead a life of fulfillment.