The document discusses health and illnesses. It defines health as a state of physical and social well-being, while illnesses are health problems that affect the body's organs. It outlines different types of illnesses and diseases, their causes and symptoms. Infectious diseases are caused by microorganisms like bacteria, viruses, protozoans and fungi. Non-infectious diseases include allergies, malnutrition, and mental illness. The document also provides tips for preventing infectious diseases through healthy lifestyle habits and vaccinations.