Prana and ayama

If ‘prana’ refers to life force (the energy that animates the body and mind), then ‘āyāma’ means its expansion, or regulation. Yoga teaches us that the breath does something beyond gas exchange. It is the only element of the autonomic nervous system that we can consciously control — a rare point of access between the voluntary and involuntary, the conscious and unconscious.

In essence, pranayama is a way of working with the energy that shapes your internal state, through the vehicle of the breath.