Pneumonia is a type of lung infection that can be caused by bacteria, viruses, or fungi. It inflames the air sacs in one or both lungs, causing them to fill with fluid or pus, leading to symptoms such as cough, fever, difficulty breathing, and chest pain. Pneumonia can range from mild to severe and can be life-threatening, especially in older adults, young children, and people with weakened immune systems. Research in this area focuses on developing better diagnostic tools, vaccines, and treatments to improve outcomes for patients with pneumonia.