There are three different types of kapalabhati. In the case of vatakrama kapalabhati, exhalation is forced while inhalation is natural and passive. Vyutkrama kapalabhati sees water sniffed in through the nose and then spat out through the mouth. Finally, sheetkrama kapalbhati is when water is taken in the mouth and then forced out through the nose.
This practice is carried out in order to cleanse the nasal passages and respiratory system, which prepares the practitioner for kapalabhati pranayama (skull shining breath) or any other of the various yogic breathing techniques.