Pranayama is all about the breathing and concentrating the mind. It is the measuring, control, and directing of the breath. Pranayama controls the energy within the organism, in order to restore and maintain health and to promote evolution.
Pranayama gives control of breathing processes and control of vital force. When the inflowing breath is neutralized or joined with the out flowing breath, then perfect relaxation and balance of body activities are realized. In yoga, we are concerned with balancing the flows of vital forces, then directing them inward to the chakra system and upward to the crown chakra.
Pranayama or breathing technique is very important in yoga. It goes hand in hand with the asana or pose. In the Yoga Sutras, the practices of pranayama and asana are considered to be the highest form of purification and self discipline for the mind and the body, respectively. The practices produce the actual physical sensation of heat, called tapas, or the inner fire of purification. It is taught that this heat is part of the process of purifying the nadis, or subtle nerve channels of the body. This allows a more healthful state to be experienced and allows the mind to become calmer.