Hatha yoga is the physical practice postures techniques known in Sanskrit (the language of Yoga) as asana and pranayama. It is a generalised term that covers Iyengar, Astanga and many other forms.
Iyengar yoga places special focus on developing strength, endurance and correct body alignment in addition to flexibility and relaxation. Iyengar yoga is meditation in action. As students practise asanas the mind is focused on the actions of the posture and the movement of the breath. As the mind unites with the body and the breath students move into a meditative state. As the practice continues, a student's ability to relax and to concentrate improves and inner awareness is enhanced.
Astanga or Ashtanga yoga involves synchronizing the breath with a progressive series of postures - a process producing intense internal heat and a profuse, purifying sweat that detoxifies muscles and organs. The result is improved circulation, a light and strong body and a calm mind.
In Viniyoga, the body, breath and mind are linked through physical practice, with the breath movement initiating the body movement. The emphasis on precise breathing and the introduction of sound into asana practice are unique features of Viniyoga.
Bikram yoga uses a sequence of twenty-six hatha yoga postures to systematically move fresh, oxygenated blood to each cell, restoring all systems to healthy working order. Bikram is practised in studios heated to 100 degrees Fahrenheit to simulate the Indian climate. Proper weight, muscle tone, vibrant good health and a sense of well-being will follow.
Kundalini yoga believes the key to the unconscious mind lies at the base of the spine. It intends to force energy up from the spine stimulating the Chakras (energy centres) and improving awareness. Breath, sound and meditation are the main resources of Kundalini yoga.
Tantra yoga suggests that external stimuli, including sexuality, are a very powerful force that can be harnessed for increased self-awareness.
Kriya yoga suggests that we are a miniature version of the whole cosmos, a microcosm - an evolving universe within the macrocosmic world. Yoga is the means of conjoining this correspondence between microcosm and macrocosm - realising the truth behind the union of individual self and the Supreme self.