There are three elements or qualities of pranayama. They are the following:
Desha, which refers to where you are focused mentally.
Kala, the equal ratio in pranayama between the inhalation, exhalation, and retention.
Samkhya, which refers to the pattern of breathing or length of time spent practicing pranayama
The great advantage to practicing pranayama is that it revitalizes the body as well as the mind. It leads to a sense of well-being and clarity.
The effects of pranayama can be physical as well as psychological, and it is always advisable to have a yoga teacher instruct you with the breathing practices before adopting them on your own. Advanced pranayama practices are powerful tools for raising energy and should always be guided by a knowledgeable teacher.
Want to know more about breathing, and not just for yoga? Check out Donna Farhi's The Breathing Book, a comprehensive work on the right and wrong way to breathe.