Pranayama

The Sanskrit term prāṇāyāma or pranayama or pranayama (‘breath control’) designates the breathing exercises of yoga that lead to concentration and control of prana (energy contained in the breath within the body).

Etymology
The Sanskrit term pranayama means ‘breath control’ 

prāṇá: air, breath, life, inhaled air, life force 
yama: control

According to some yoga groups, pranayama would mean ‘expansion of the breath’:

prāṇá: breath;
āiāma: stretch, extend; having; expanding the length (in space or time), the duration of a breath
Prana
{{AP|Prana (Hinduism)}

Practice
During the time of sandhia (the divisions of the day: sunrise, noon and sunset) three ‘breathing exercises’ are performed which are:

– puraka
– rechaka
– kumbaka

Source: Wikipedia