Sri Aurobindo identifies three principles that form the basis of practice for all forms of Yoga, including Hatha Yoga. These three are purification, concentration and liberation. Purification provides basic preparation for the instrument by removing obstructions from the practice of Yoga and helping prepare it for the energy influx that needs to be held and modulated with the later steps. Concentration focuses the attention and gathers the energy. Liberation results from the purification and concentration steps so that the human instrument is undistracted, focused and able to seat itself in consciousness outside the narrow bands of human activity motivated by desire and revolved through the action of the three Gunas.
Sri Aurobindo observes: “first, purification, that is to say, the removal of all aberrations, disorders, obstructions brought about by the mixed and irregular action of the energy of being in our physical, moral and mental system; secondly, concentration, that is to say, the bringing to its full intensity and the mastered and self-directed employment of that energy of being in us for a definite end; thirdly, liberation, that is to say, the release of our being from the narrow and painful knots of the individualized energy in a false and limited play, which at present are the law of our nature.”
The result is: “The enjoyment of our liberated being which brings us into unity or union with the Supreme, is the consummation; it is that for which Yoga is done.”
Hatha Yoga shares these principles and the intended result with the other paths of Yoga.
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 27, Hathayoga, pg. 508