Ashtanga yoga is a system of asanas and vinyasas. Asanas are yoga postures strung together in a specific order with clearly defined movements. These movements occur simultaneously with either an inhale or exhale between postures, and these movements with breath are called vinyasas. Other forms of vinyasa yoga all stem from Ashtanga.
There are different sequences which we group together to form a practice, usually lasting from about 45 minutes to 2 hours. Each practice begins with sun salutations and fundamental standing postures. Then one could add part of, or a whole series, such as primary or intermediate series. Next, we do backbends, and for a counter pose to this backbending, a forward fold. Lastly comes a closing sequence and resting time.
All asanas (postures) are strung together in a specific sequence which moves the body in an intelligently designed way. Many asanas have counter-asanas. In the closing sequence, we have 7 progressive shoulder stands with Matsyasana (the fish posture) serving as counterpose to the shoulder stands. In shoulder stands, the head is placed forward toward the chest – the chin is very close to the clavicles with the spine moving straight upward. With Matsyasana, the head tilts way back away from the chest with the spine curving forward in a deep upper backbend shape. Many asanas have fascinating myths and stories surrounding them.
Matsyasana, the fish posture (pictured in the header image above) has one of my favorite legends connected to it. As with many mythical stories from all over the world, there are many versions, but here is a nice one as told by Amy Vaughn:
Lord Shiva and the Goddess Parvati as a single entity