Pepperoni is a common topping for pizza made out of beef or pork. It is considered a type of sausage and can be mildly spicy. Pepperoni pizzas are cheese pizzas with pepperoni on top or underneath the cheese. It is the most common and popular pizza topping.
Pepperoni originally came from Italy where it was a type of salami made from fermented pork. In the United States, it is often made out of beef, or a beef and pork mix. The nomenclature behind the name pepperoni is a convoluted corruption of the Italian word for bell peppers. In turn, it came to refer to spicy foods in general and eventually came to refer to pepperoni proper. In Italy it is called sallame piccante.