Peperoni are bell peppers, here shown as Peperoni Arrostiti, roasted peppers. They can also be grilled, and in season often appear with other seasonal vegetables in the side dish called grigliata mista di verdura, a mixed grill of vegetables. They can also be chopped raw with other vegetables and lettuce into insalata mista, a mixed salad.
This is what you’ll get when you order peperoni pizza. You were expecting the American Pepperoni? It doesn’t exist as such in Italy. Pepperoni is salame piccante or spicy salame in Italian.