Chronic obstructive pulmonary disease is one of the most common lung diseases,which there is a chronic obstruction to airflow due to chronic bronchitis/emphysema.This cannot be relieved by bronchodilators. There are two main forms

1)Chronic bronchitis :This is the condition in which involves small bronchioles with chronic cough and phlegm.
2)Emphysema : This is the condition in which involves destruction of lungs and enlargement of the lung alveoli.

Most people have a combination of both these conditions.

Causes :
-Smoking
-Pollution
-Exposure to certain gases Rarely
-it occurs in non-somokers who lack protein alpha-1 antitrypsin can develop emphysema.
-Smoke when you cook/burn.

Symptoms :

-Cough, with or without mucus
-Fatigue
-Many respiratory infections
-Breathing difficulty (dyspnea)
-Wheezing

Treatment:

There is no cure for COPD. Only thing is to relieve symptoms and avoid causing agents.
Medications such as  Inhalers(bronchodilators),nebulizing with medicine,steroids through mouth/vein,Oxygen mask therapy,Anti-inflammatory medications, Antibiotics, these helps to open the air sacs,so that you can breath without much difficulty.