In developing nations, pneumonia is the leading cause of death for young children; however, mortality can be effectively decreased with early diagnosis and care. The objectives of the review are to evaluate the significance of clinical signs and symptoms in diagnosing pneumonia, and treatment in children under the age of five, as well as to examine the precision of WHO criteria in diagnosing clinical pneumonia in general people. According to the World Health Organization's definition and the Integrated Management of Childhood Illness (IMCI) initiative, pneumonia is clinically characterized by an acute cough, with or without fever, accompanied by dyspnea or tachypnea. Acute infections of the gut and gastroenteritis can be effectively controlled and treated. Acute respiratory infections, particularly pneumonia, are increasingly regarded as the leading infectious cause of mortality among children in developing nations. The diagnosis of pneumonia is primarily clinical and categorized into four domains: clinical assessment, epidemiological factors, radiographic imaging, and standard laboratory results. Pneumonia can be classified into three categories: bacterial, viral, and acute pneumonia. In every instance, a potential diagnosis should be made and the appropriate course of therapy should be administered based on the features of that pneumonia. Preventing and lowering the death and morbidity of this significant disease in children can be greatly aided by physicians having precise and accurate information on how to identify and treat it without incurring additional expenses.