Kapalbhati is a breathing exercise i.e. one of the six SHATKARMA Kriya (Body Cleansing technique). Some Yog Sadhaks consider it as a Pranayam.
"Kapal" means Head/ Skull and "bhati" means shining. In this process, the organs under the skull mainly the brain and the small brain are influenced in a good manner.
In shatkarma Kaplabhati used to throughout toxins from Kapal(Head) and simultaneously from Lungs and stomach.

Benefits:
IT Cleans your body by removing toxins and CO2 and helpful in Kundlini Jagran.
Helpful in disorders of Respiration and Digestive System.

Precaution:
Do not practice in case of Pregnancy, Hernia, Peptic Ulcer and if surgery done in last 6 months.
In case of Heart Troubles, lung troubles, Hypertension and High BP ,Practice under supervision of Expert.