Pranayama refers generally to what aspect of yoga?
Pranayama century Hatha Yoga Pradipika is a key text of this tradition and includes various forms of pranayama such as breath retention techniques termed Kumbhaka and various body locks (Bandha). Other forms of pranayama breathing include Ujjayi breath ("Victorious Breath"), Bhastrika ("bellows breath") and Kapalabhati ("skull shining breath"). Many of these practices have become popular in Western forms of Yoga. According to the Pali Buddhist Canon, the Buddha prior to his enlightenment practiced a meditative technique which involved pressing the palate with the tongue and forcibly attempting to restrain the breath. This is described as both extremely painful and not conducive
Pranayama 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. Many yoga teachers advise that pranayama should be part of an overall practice that includes the other limbs of Patanjali's Raja Yoga teachings, especially Yama, Niyama, and Asana. The Indian tradition of Hatha Yoga makes use of various pranayama techniques. The 15th