While cancer is a disease commonly associated with smoking tobacco, Chronic Obstructive Pulmonary Disease is the third-leading cause of death in the United States, and smoking is the leading cause of COPD.  Other causes of COPD include genetic problems such as alpha-1 antitrypsin deficiency, long term lung damage stemming from premature birth, and exposure to lung irritants such as chemicals and fumes.  Most often, COPD is broken into two categories: emphysema and chronic bronchitis. However, people with COPD most often have a combination features associated with both diseases. Chronic obstructive pulmonary disease can be treated and lung damage halted, but once lung damage develops it is permanent and cannot be reversed.
To get oxygen to our bloodstream, it must pass through tiny air sacs called alveoli—there are hundreds upon hundreds of these little bubble-like alveoli in our lungs. In emphysema, the alveoli become stretched out and larger than they should be. This makes exchanging oxygen for carbon dioxide difficult, as air becomes trapped in the alveoli. This causes shortness of breath and exercise intolerance, and sometimes coughing and wheezing.  Because the body cannot exchange enough oxygen, low oxygen saturation may develop and cause problems with the heart, as well as with cognitive processes, including impaired thinking. 
About chronic bronchitis
In chronic bronchitis, the airways produce more mucus than normal, and the airways become irritated and narrower.  Damage to the bronchioles (breathing tubes) in the lungs develops, making them smaller than they should be, causing shortness of breath, coughing and wheezing. Like with emphysema, if untreated, low oxygen saturation can cause problems with the heart and brain.
Often people have a combination of emphysema and chronic bronchitis. With both, the earlier it is treated, the less damage will happen to the lungs.
Asthma-COPD Overlap Syndrome
A relatively new condition being explored, Asthma-COPD Overlap Syndrome (ACOS) means a person has both symptoms of asthma and COPD. Unlike in asthma where lung function returns to normal when asymptomatic, people with ACOS have reduced lung function all the time, which may worsen periodically in flare-ups, like with asthma. 
ACOS is hard to study because of the similarities between asthma and COPD. More research into ACOS needs to be done to understand it better.
The most important thing that people with COPD can do is to quit smoking to make breathing easier, but lung damage will be permanent once COPD has developed. COPD is treated with inhaled medicines to keep the airways in the lungs open and decrease inflammation—sometimes oral corticosteroids may also be used to treat lung inflammation. Antibiotics may be needed continually or as needed, as increased mucus in the lungs may lead to frequent infections, causing breathing to become more difficult. In many cases, low oxygen saturation (oxygen levels in the blood) is a problem, and oxygen therapy —where oxygen is delivered via a tube into the nose (nasal cannula), via a mask into the nose and mouth, or through a tube via a small hole made in the trachea, low on the neck (transtracheal oxygen). People with COPD usually have to check their oxygen levels regularly. As well, Pulmonary Rehabilitation is an important part of COPD treatment. Pulmonary Rehabilitation helps people become more physically fit through exercise, enabling them to more easily participate in the things they want to do. Exercise can help the lungs work better and improve quality of life.
Reduce Your Risk
Avoiding smoking and second hand smoke is the easiest way to prevent most forms of COPD. While COPD is not always preventable, as is the case of genetic disorders, it can be treated. If you have COPD, wearing a COPD medical bracelet, lung disease necklace, or emphysema alert bracelet can help you get the treatment you need in a medical emergency. Check out our medical ID bracelets and necklaces.