Pranayama is the manipulation of the life force energy (or chi ) using the breath. The idea is to acheive optimum health by manipulating the pranic rhythms of the body.
Pranayama has great health benefits. It is also helps one reach higher states of self awareness. It is usually practiced before meditation. However, pranayama is considered a form of meditation too. The practice of pranayama can help impact the mind is a way similar to meditation.
Speaking of prana, there are five types that govern the proper functioning of the body, namely prana, apana, vyana, udana and samana. According to tradtional yoga texts, such as the Hatha Yoga Pradipika, there are two of these five that are significant on a physical, day-to-day level. They are prana, which flows upward and apana, which flows downward. The practice of pranayama is said to initiate balanced functioning of the body.
There are several categories of pranayama such as deep breathing, fast breathing, breathing with the use of sound and so on.
Some of the commonly practiced types of pranayama include Nadi Shodhana or alternate nostril breathing Anuloma-viloma, also alternate nostril breathing, done pscyhically (that is without using the mudra to manipulate the nostrils) ujjayi or the hissing breath brahmari or the bee humming breath sheetali or the cooling breath Bhastrika or the bellows breath
Pranayama is an efficient way to cleanse the body of waste. One important aspect of pranayama is breath retention. According to yogic literature, breath retention enables an increase in the flow of prana throughout the body, keeping it youthful and healthy in the process. However, breath retention is not to be practiced under certain circumstances including pregnancy and high blood pressure.
Please consult an experienced yoga teacher before you start practicing pranayama.