Hatha yoga, pronounced "ha-tuh", is also known as hatha vidya or the "science of hatha" yoga; this word comes from combining the two sanskrit terms "hat" meaning sun and "ha" meaning moon. The word "hat" refers to the solar nadi (pingala) in the subtle body and "ha" the lunar channel (ida). Hatha yoga is what most people associate with the word "yoga."
Hatha yoga primarily concerns itself with asanas or postures. Asanas are contemplative in nature and were originally intuited by yogis during meditation; the Kundalini naturally brings forth these postures or movements, called Kriyas, during deep meditation. These movements help to remove blockages (disease) in the causal, subtle, and physical bodies.
When the emotions are calm, i.e. the subtle body is clear, the mind becomes tranquil and meditation occurs naturally. As a result of these enlightened sages' insights, the practice of hatha yoga developed for people who had not refined their intuition to the point of "knowing" what asanas their bodies needed. Although Gorakhnath is considered by many to be the founder of Hatha Yoga it is more likely that he was the first person to write down what he had been taught by his teacher and intuited during meditation.
