Pneumonia: Understanding Inflammation of the Lungs - Causes & Symptoms

Pneumonia is inflammation of the lungs. The lungs are two large organs in the chest that are responsible for breathing. They are made up of millions of tiny air sacs called alveoli, which are where oxygen from the air we breathe is transferred into our bloodstream. When the alveoli become inflamed, they fill with fluid or pus, making it difficult to breathe.