Now let's talk about what pneumonia is and its classification. Pneumonia refers to inflammation of the terminal airways, alveoli, and pulmonary interstitium. It can be caused by pathogenic microorganisms, physicochemical factors, immune damage, allergies, and drugs. Bacterial pneumonia is the most common type of pneumonia and is also one of the most common infectious diseases. The classification of pneumonia generally involves several aspects: First is the anatomical classification: from an anatomical perspective, it can be divided into lobar pneumonia (alveolar pneumonia), bronchopneumonia (bronchial pneumonia), and interstitial pneumonia. Second, the classification based on etiology, which mainly includes the following aspects. The first is bacterial pneumonia, which includes Streptococcus pneumoniae pneumonia, Staphylococcus aureus pneumonia, Klebsiella pneumoniae pneumonia, Haemophilus influenzae pneumonia, Pseudomonas aeruginosa pneumonia, and Acinetobacter baumannii pneumonia, etc. The second point is pneumonia caused by atypical pathogens such as Legionella, Mycoplasma, and Chlamydia. The third is viral pneumonia. The fourth refers to fungal diseases or fungal pneumonia. The fifth is pneumonia caused by other pathogens: such as rickettsiae, parasites. The sixth is pneumonia caused by physicochemical factors: such as radiation pneumonia, inhalational pneumonia, and lipid pneumonia. The third category is classification by the environment of illness, which can be divided into two types: the first is community-acquired pneumonia, and the second is hospital-acquired pneumonia.