Pepperoncini is a pepper type like a bell pepper or a chili pepper. There are a lot of recipes that use pepperoncini like stuffed pepperoncini. They can also be used in salads, sandwiches or in pasta dishes.
Pepperoncini are ingredients for a recipe, not a recipe themselves. They are a type of Italian pepper, usually found in jars on the pickle aisle of your supermarket. You can get them either pre-sliced or whole.