This is all about Diaphragmatic Breathing. - breathing that is done by contracting the diaphragm.
The aim of this breathing is when air enters the lungs, the chest does not rise and the belly expands during this type of breathing.
This type of breathing has so many benefits for the body. It is a great breathing technique to learn so it becomes a habit of yours to use anytime you feel slightly overwhelmed or stressed. It helps you relax lowering the harmful effects of the stress hormone cortisol on your body. It lowers your heart rate. It slows your rate of breathing so that it expends less energy.
This technique is SO VALUABLE.