In diaphragmatic breathing, you actively expand the abdomen during inhalation. The abdominal expansion occurs via the diaphragm contracting and pressing down on the abdominal contents. Chest expansion is kept at a minimum in this type of breathing. Exhalation is a relaxed process and occurs through the elastic recoil of the chest wall and lungs.Regular practice of diaphragmatic breathing draws the mental focus into what is known as the “belly brain”. It has a calming effect on the mind while, at the same time, potentially strengthens the diaphragm. I recommend practicing diaphragmatic breathing for 5-10 minutes per day. We have included a video link below to guide your practice and aid you in visualization of the movement of the diaphragm and abdomen.
Source: The Daily Bandha: Diaphragmatic (Belly) Breathing
Check the video in the link. Very interesting stuff.