Hatha yoga, also known as Hatha vidya, is a particular system of Yoga introduced by Yogi Swatmarama, a sage of 15th century India, and compiler of the Hatha Yoga Pradipika. The word Hatha is a compound of the words Ha and Tha meaning sun and moon and refers to the principle nadis (energy channels) of the subtle body that must be fully operational to attain a state of ultimate peace, called bliss. In other respects Hatha yoga also includes moral restraint and spiritual observances. Hatha Yoga is what most people in the West associate with the word "Yoga" and is practiced for mental and physical health throughout the West.
The main component of hatha yoga is yoga postures, or, in Sanskrit, asanas. The word asana means comfortable, stable pose. Asanas are exercises of a special kind. The form that they have taken is the result of a thousand years of experience: trial and error, experiments, and scrupulous observation. The yogis have discovered that certain positions of the body can give human beings qualities that they do not have or that are in deficitAsanas are special positions of the body that strengthen, provide proper alignment, purify and balance the endocrine, nervous and circulatory systems and should not be confused with mere exercise, calisthenics, which help strengthen and develop muscles. While asanas are rarely prescribed to treat illnesses, they surely have healing properties and definitely prevent diseases. Many healers use asanas and other hatha yoga methods to effectively treat chronic illnesses and emotional disorders. If you practice asanas regularly, your body will gradually achieve greater endurance, your spine will become more flexible, your body will come to its natural weight and rid itself of toxins, you will breathe more easily, you will gain energy, your circulation will improve, your blood pressure will normalize, you will have an easier time coping with stress, and you will have more pleasant thoughts and fewer negative emotions. And considering all this, your overall mood will improve—in other words, you will gain vibrant physical and emotional health.