Why does milk, and not water, keep spicy foods from burning?

What makes spicy foods spicy? What is the Scoville Heat Scale? What are the spiciest peppers in the world? For free home activities sign-up at www.WhoSmarted.com See Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.