The document discusses health and illness. It states that when we are healthy we feel well, while illness is the opposite and makes us feel bad, with symptoms telling us our bodies are ill. It lists behaviors to maintain health such as getting enough sleep, eating a balanced diet, washing hands, and getting fresh air. It also explains that infectious illnesses are caused by bacteria or viruses and can be contagious or non-contagious, being transmitted from person to person in the case of contagious illnesses like the flu. Pathogenic microorganisms can enter the body through the respiratory, digestive, or skin systems.