Lung cancer is a type of cancer that starts in the lungs, typically in the cells lining the air passages. It is often linked to smoking but can also occur in non-smokers due to other factors like genetics or exposure to carcinogens. Symptoms may include persistent cough, chest pain, shortness of breath, and coughing up blood. Treatment options depend on the type and stage of cancer but may include surgery, chemotherapy, radiation therapy, targeted therapy, or immunotherapy. Early detection through screening can improve outcomes.