Infectious diseases are caused by germs like bacteria, viruses, fungi, or parasites. These diseases can spread from one person to another, or through air, water, food, or insect bites. Examples include the flu, COVID-19, and tuberculosis.

Non-infectious diseases are not caused by germs and do not spread from person to person. These are usually caused by genetics, lifestyle, environment, or aging. Examples include diabetes, heart disease, and cancer.

In short, infectious diseases are contagious and caused by outside organisms, while non-infectious diseases are not contagious and come from other factors inside the body or environment.