Pranayama is a form of yoga, which helps you to maintain the control of breath. Pranayama empowers you with the control of breath. It also helps you to control the way in which the energy functions thus achieving a balance between body and mind.
Prana means the most important energy and Ayama means control thus Pranayama means control of energy through disciplined methods.

Holding breath is a very important practice that has been existing since ancient times and has been a major part of reaching Samadhi. In fact, in the Hatha Yoga there are eight kinds of pranayama, which stabilize our body and mind. The main aim of pranayama is to increase the force of life so that one can reach the gaps in the brain thus stopping any kind of degeneration.

Technique :

Be seated in a meditative position.
Stay erect and sit with your knees folded.
Breathe naturally and feel air passing in and out of the lungs.
You should breathe from the abdomen while taking breath.
Inhale with the walls of the abdomen moving out and exhale by letting the abdomen move in.
Remember to inhale and exhale with a clear mind and relax your mind, body, and soul while performing this yoga method.

Benefits :

It gives a great form of relaxation and eases out the mind as well as the body.
It helps in strengthening the nervous system and the respiratory system.
Pranayama is a good form of improving concentration.
It helps in relieving Hypertension, Depression, and Stress.

When to Practice Pranayama :

Pranayama has to be practised after proper medical permission from the doctor.
It should be done only after you have gained control over all the yoga asanas.
If you have had a meal practise pranayama three hours after your last meal.

Precautions & Tips :

Remember to breathe through the nose always.
There is a certain rhythm to be maintained during pranayama.