Pneumonia: Some fluids you just don't want in your body!

 First and foremost pneumonia is an infection of the lungs. Many different germs can cause pneumonia, including bacteria, viruses, and fungi. When you breathe in these germs, they can settle in the air sacs (alveoli, which is connected to the bronchioles, bronchi and trechea etc.) of your lungs. Deep in your lungs, the germs may grow and overcome your body's normal defenses.
After they become infected, the air sacs then fill with pus and mucus. This swelling (inflammation) of the air sacs makes them less stretchy and keeps oxygen from properly reaching your blood stream.
As you work harder to breathe and give your body oxygen, you can feel short of breath. It usually effects people who are more susceptible like infants and seniors, or people who have previously had a flu or cold and their immune system is weaker.

here is a video that will leave you with a further understanding!