Chronic bronchitis is defined as a productive cough that lasts for three months or more per year for at least two years. Tobacco smoking is the primary cause and leads to chronic obstructive pulmonary disease in most cases. Symptoms include a chronic cough with mucus, wheezing, and shortness of breath. Treatment focuses on quitting smoking, using inhaled bronchodilators and steroids, and addressing exacerbating factors through medications, oxygen therapy, or lung transplantation in severe cases.