Chronic Obstructive Pulmonary Disease refers to a problem with breathing air out from your lungs. Until recently, most people who had COPD were grouped together and considered to have one disease.  We now know that several different diseases cause this difficulty in releasing air from the lungs.  Asthmatic bronchitis, chronic bronchitis, and emphysema are three of the major diseases that are grouped together as COPD. Thus, COPD is not just one specific disease but a group of diseases which all cause difficulty breathing.