This lesson explains that health means being physically, mentally, and emotionally well, not just free from illness. Diseases are conditions that make our bodies work improperly and can be caused by germs, poor nutrition, or environmental factors. Communicable diseases, like flu and chickenpox, spread from person to person through sneezes, coughs, touch, or sharing items, and highly spreadable ones are called contagious diseases. Examples include polio, TB, COVID-19, and the flu, which can often be prevented by washing hands, covering coughs, and staying home when sick. Non-contagious diseases, such as diabetes and cancer, do not spread between people and may be linked to lifestyle, body functions, or environmental causes. The key to staying healthy is good hygiene, vaccination, and healthy living habits.