Bronchitis is an inflammation of the bronchial tubes, which carry air to and from the lungs. It can be acute, often caused by viral infections like the flu or cold, or chronic, typically resulting from long-term irritation such as smoking. Symptoms include coughing, mucus production, wheezing, and difficulty breathing. Treatment may involve rest, hydration, and medications to alleviate symptoms and, in chronic cases, lifestyle changes to reduce exposure to irritants.