Asana is the third accessory of ashtanga yoga Asana means a seat. Asana is a state where the individual continues to settle down. Asana is a place that is occupied.
Generally, people think that if they practice asana, they are doing yoga, though asana is a part of yoga. They do a lot of physical movements and call these movements also as their yoga practice.
Shareera, the human body is not a mere physical body. The human body is a complex system and is made up of three bodies, - the gross body, the subtle body and the causal body.