The word ‘yoga’ is derived from the Sanskrit word ‘yuj’, which means to join, bind, or direct/concentrate the attention for meditation. Yoga can be thought of as the art of bringing together a scattered mind as well as uniting body with mind.
With asana we create a physical body where energy can flow easily and efficiently throughout the body. Through pranayama we learn how to control the flow of this energy.
According to the sutras of Patanjali, there are 8 stages in reaching a unified state of being. These are: yama (abstinence); niyama (observances); asana (posture); pranayama (breathing), pratyahara (withdrawal); dharana (concentration); and dhyana (meditation); and finally, samadhi (absorption).
Within the context of modern-day concepts of mental and physical wellbeing, we are primarily concerned with stages 3, 4 and 5 (asana; pranayama; and pratyahara).
Where asana are the physical postures and movements that open and purify the body, pranayama is the prolongation of the breath to create a steady mind, strong will, and control energy flow. Pratyahara is the process and act of bringing mind and senses under control.