What does it mean to suffer from pneumothorax?

A hole in your lung : Put your fist in a slightly inflated balloon. Your fist is your lung. The balloon represents the lung lining both inner and outer. The space inside is where a small amount of fluid lives. When the outer balloon is punctured by something (broken rib, ect), air pushes down onto your lung, and your lung 'drops'. We place a little tube into that space to re-inflate your lung, allowing healing.

Lung leak into chest: A collapsed lung (pneumothorax) is due to an air leak from the inside of the lung through the covering of the lung, out into the space between the lung and the ribs. The site of the leak has some damage, which will heal itself later. But the leak may continue, with leaked air filling the rib cage (chest cavity), pushing on the heart and collapsed lung...Causing death. Pneumothorax is an emergency.