COPD is a lung disease that makes breathing difficult by narrowing the airways. Smoking is the main cause of COPD. There are 4 stages of COPD that get progressively more severe, with stage 4 being life-threatening. Symptoms include coughing, shortness of breath, weight loss, headaches, and fatigue. While there is no cure for COPD, treatment focuses on quitting smoking, medications, and lifestyle changes to manage symptoms and slow disease progression.