What is Asana?
When most people think of yoga, they think of Asana, a type of physical posture or pose.
Asana means seat. In Asana, the body becomes the seat of Purusha, or pure consciousness. This is the fundamental idea of Asana, and with this idea, a physical posture actually becomes a means of Yoga.
The experience of Asana is an experience of deep meditation in each moment of any yoga pose. This is the result of every single part of the body functioning congruently and in complete unison to perform the Asana. This complete integration of all parts into a single unified organism performing a task is true Asana.
The idea of effort or difficulty in any yoga pose is simply an indication of lack of physical integration when performing the pose.
Asana, therefore, is a means of experiencing physical integration, or yoga. Asana offers an opportunity to experience a gross form of integration, or yoga, which gradually gives rise to the experience of deeper levels of integration within the individual.
When performed correctly, Asana affects the entire physiology (Koshas), the physical body, as well as the Prana, the mind, intellect and the samskaras.
प्रयत्नशैथिल्यानन्तसमापत्तिभ्याम् ॥ ४७ ॥
"When effort relaxes, the experience of eternal awareness happens, and Asana is mastered."
-Yoga Sutra 2.47