PUL stands for PolyUrethane Laminate, and refers to fabrics (generally cotton or polyester) that have had a thin layer of "plastic" bonded to one side. This creates a waterproof fabric that is often used as the waterproof layer in cloth pads. ProCare is a type pf PUL that has the laminate completely on one side, like standard PULs, but also partially on the other side, due to the method of manufacture.
There is some debate as to how "breathable" this fabric is. It was created for uses such as waterproof raincoats, where it was designed to allow a small amount of airflow (microscopically small) to avoid condensation and "sweaty" feelings while wearing it. So comparing it to a PVC or other "plastic" fabrics, it is more "breathable". However comparing it to a natural fabric, or a looser weave fabric like synthetic fleece, it is not as "breathable".