Bronchitis is an inflammation of the mucous membranes of the bronchi (the larger and medium-sized airways that carry airflow from the trachea into the more distal parts of the lung parenchyma) characterized by discharge of yellowish grey, white or green mucous.
It is divided into two types:
Acute bronchitis is usually caused by viruses, typically the same viruses that cause colds and influenza. Antibiotics don't kill viruses, so this type of medication isn't useful in most cases of bronchitis. The most common cause of chronic bronchitis is smoking cigarettes. Air pollution and dust or toxic gases in the environment or workplace also can contribute to the condition.
Note: We are giving only a brief description of each disease for your quick reference with some best related photographs where needed.