Stromboli is a type of turnover

Turnover (food)

A turnover is a kind of pastry made by placing a filling on a piece of dough, folding the dough over, and sealing it. Turnovers can be sweet or savory and are often made as a sort of portable meal or dessert, similar to a sandwich....

 filled with various cheese

Cheese

Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....

s, typically mozzarella

Mozzarella

Mozzarella is an Italian Traditional Speciality Guaranteed food product. The term is used for several kinds of Italian cheeses that are made using spinning and then cutting :...

, Italian meats

Cold cut

Cold cuts are cheeses or precooked or cured meat, often sausages or meat loaves, that are sliced and usually served cold on sandwiches or on party trays. They can be bought pre-sliced in vacuum packs at a supermarket or grocery store, or they can be purchased at a delicatessen or deli counter,...

 such as salami

Salami

Salami is cured sausage, fermented and air-dried meat, originating from one of a variety of animals. Historically, salami has been popular among Southern European peasants because it can be stored at room temperature for periods of up to 10 years, supplementing a possibly meager or inconsistent...

, capicola

Capicola

Capocollo , or coppa, is a traditional Calabrian Italian cold cut made from pork shoulder or neck, and dry-cured whole. The name coppa is Italian for nape, while capocollo comes from capo—head—and collo—neck—of a pig. The Italian spelling, "capocollo'", is derived from Latin, "caput collum"...

 and bresaola

Bresaola

Bresaola or brisaola is air-dried, salted beef that has been aged two or three months until it becomes hard and turns a dark red, almost purple colour. It is made from top round, and is lean and tender, with a sweet, musty smell...

 or vegetable

Vegetable

The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....

s. The dough

Dough

Dough is a paste made out of any cereals or leguminous crops by mixing flour with a small amount of water and/or other liquid. This process is a precursor to making a wide variety of foodstuffs, particularly breads and bread-based items , flatbreads, noodles, pastry, and similar items)...

 is Italian bread dough.
A stromboli is made with a square shaped pizza dough that can be topped with any pizza toppings and is then rolled into a log and baked.
There are several theories regarding the origin of the Stromboli. It may have originated in 1950 in Essington, Tinicum Township

Tinicum Township, Delaware County, Pennsylvania

Tinicum Township, more popularly known as "Tinicum Island" or "The Island", a census-designated place and township in Delaware County, Pennsylvania, United States. The population was 4,353 at the 2000 census. Included within the township's boundaries are the communities of Essington and Lester...

 just outside of Philadelphia, at Romano's Italian Restaurant & Pizzeria, by Nazzareno Romano.