Anchovies are a family of small, saltwater forager fish. They are preserved in brine, matured, and packed in oil or salt.
Anchovies are a common topping for pizza. It can be assumed that the use of anchovies as a pizza topping dates back several hundred years, as anchovies are a common addition to a variety of European dishes.
Many pizza restaurants no longer offer anchovies as a topping, as they have fallen out of favor in recent years. They can most commonly be found in "gourmet" pizza restaurants, or at higher-end restaurants that serve pizza, although some restaurants such as Papa John's still offer anchovies as a topping.