Gorakhnath (often called Goraksha, Gorakshanath, or simply Gorakh) is an elusive figure historically. He is many things to many people.
Gorakhnath is traditionally said to be the originator of Hatha Yoga, the yogic system of asanas (physical postures) that are part of the Tantric alchemical process of physical perfection and energetic awakening.
He is one the semi-divine Siddhas and is considered to be the founder of the Nath Siddha lineages, the supreme guru of the Gorakhnathi Jogis. For some Gorakhnath is no less than an incarnation of Shiva himself.
Gorakhnath is also a lineage bearer of Buddhist Tantra in Tibet.
Gorakhnath is said to be the author of the Goraksha Paddhati (“Track of Goraksha” — also called the Goraksha Samhita, a foundational treatise on esoteric Hatha Yoga, translated in Georg Fuerstein’s excellent book The Yoga Tradition), Goraksha Shataka (“Goraksha’s 100 Verses”) , and several other works.
A traditional story is told about the appearance of Gorakhnath. He was not born in the normal sense. A holy man named Matsyendranath used to go door-to-door to beg for food and, in exchange, offered blessings and wisdom. At one house, the woman asked if she would ever have a child. Matsyendranath gave her some holy ash and said if she swallowed it she would have a child. The woman told her neighbor who derided her naivete in believing such things, so she threw the ash away on a dung heap. Twelve years later, Matsyendranath returned and asked how the child was doing. The woman confessed what she had done with the ash. The holy man went to the dung heap and prayed, calling to the boy. A beautiful 12-year-old boy emerged. Matsyendranath took the boy with him. That boy was Gorakhnath.
The name Gorakh means “protected by the earth,” since it was the earth, in the form of a dung heap, that nurtured him.