Lung cancer is a disease that affects the lungs in our body. Our lungs help us breathe and take in oxygen. Sometimes, when people smoke or are exposed to harmful substances in the air, it can cause damage to the cells in their lungs. These damaged cells can grow and form a tumor, which is like a lump. This tumor can make it hard for the person to breathe and feel sick. Doctors can try to remove the tumor or give special medicines to help the person get better.