Pneumonia is a serious infectious disease. It is a respiratory disease known to affect the lungs and, specifically, the alveoli in the lungs. Pneumonia is known to kill children mostly, but this infection is treatable as well as preventable. There are two types(different from classes) of pneumonia, and they are viral pneumonia (caused by a virus) and bacterial pneumonia (caused by bacteria). Pneumonia affects everyone everywhere, but it mostly affects people living in South Asia and Sub-saharan Africa. We will begin with the known four stages of this infection and how it progresses from one stage to the other while getting worse within the individual carrying the disease.