Many students ask me "...what is the difference between Hatha yoga and other yoga styles...".
My short answer has always been that Hatha Yoga acts like an umbrella where other yoga styles permeate from.
Let's try to synchronise a description of Hatha yoga first. Devereux, 2002, states the meaning of Hatha to be 'the will'; 'sun/moon'; 'creative/receptive' and 'active/reflective'. To me these states of being are areas of opposition or maybe duality, a reflective surface, between the mind and the body. Unification of these prescribed actions are extremely advanced in nature with an emphasis on pranayama, bandhas and mudras (Deverereux, 2002).
The realm of modern developments, within yoga, consists of six teachings; four students of Krishnamacharya within the teachings of Ashtanga yoga in the spirit of Patanjali (Devereux, 2002). B.K.S. Iyengar and Desikachar who have been distinct in their development of yoga postures and Pattabhi Jois and B.N.S. Iyengar whoses modifications were slight and contextual (Devereux, 2002).
The following two contemporary Indian yoga masters are Sivandanda and now the late Sri Pradbupada. Their approaches did not come from the direct teachings of Krishnamacharya; rather the development of Satyananda and Bhakti yoga traditions here were Westernised.
Historical events such as these implode the diversity of yoga with a relationship bound by human temperament and the inherent synchronicity of the meaning of yoga "union".
Keep up your yoga and smile...