The conversation discusses the difference between a pandemic, an epidemic and an endemic disease. A pandemic refers to a planet-wide epidemic, whereas an epidemic is when there are more cases of a disease than usual in a specific place. An endemic disease is one that is constantly present in a population and may occur as seasonal epidemics. The speaker, Dr. Christopher Gill, explains how COVID-19 is moving from being a pandemic to being an endemic disease, similar to the flu. He also mentions that the distinction between pandemics, epidemics, and endemic diseases is often a judgment call, and that it is more helpful to understand it with common sense.