Prāṇāyāma is a Sanskrit word meaning "extension of the prāṇa or breath" or "extension of the life force". The word is composed of two Sanskrit words: prana, life force, or vital energy, (noted particularly as the breath), and ayāma, to extend or draw out. It is a yogic discipline with origins in ancient India. According to the Bhagavad-Gītā, prāṇāyāma is translated to "trance induced by stopping all breathing".
Pranayama is the fourth 'limb' of the eight limbs of Yoga mentioned in the Yoga Sutras of Patanjali. Patanjali discusses his specific approach to pranayama in verses 2.49 through 2.51, and devotes verses 2.52 and 2.53 to explaining the benefits of the practice. Patanjali does not fully elucidate the nature of prana, and the theory and practice of pranayama seem to have undergone significant development after him. He presents pranayama as essentially an exercise that is preliminary to concentration, as do the earlier Buddhist texts. I myself prefer a half an hour practice of pranayama first thing in the morning before my meditation.
There are over 50 particular Prāṇāyāma techniques and forms. Many yogateachers, me included, advise that pranayama should be part of an overall practice that includes the other limbs of Yoga, especially Yama, Niyama, and Asana.
Several researchers have reported that pranayama techniques are beneficial in treating a range of stress-related disorders, improving autonomic functions, relieving symptoms of asthma and reducing signs of oxidative stress. Practitioners report that the practice of pranayama develops a steady mind, strong will-power, and sound judgement, and also claim that sustained pranayama practice extends life and enhances perception.
While in meditation, I find to be the closest to my breath. Sometimes I feel, that breath is all there is. I can freely wander this earth and eat what I can find or what I choose. I have the illusion of freedom. But I'm not free. The very air which enters my lungs, ties me to this World (samsara) like a tree is tied by the soil or a fish by the water.
The breath gives us life, ties us here for as long as is needed for us to learn, what ever we need to learn. Then it leaves us, sets us free. Breath is our jailkeeper and our liberater. Understand the full meaning of this, and you are able to start your liberation during your lifetime.
Where the mind goes, the breath and body follows. Where the breath goes, the mind and body follows. By controlling/alternating your breathing you are effecting your mind and body. Breath IS life.