What is "American sub"?

An American sub, commonly referred to as a submarine sandwich or a sub, is a type of sandwich that is made on a long, cylindrical roll, typically made from Italian or French bread. The roll is sliced lengthwise and filled with a variety of meats, cheeses, vegetables, and condiments. Common fillings for an American sub include ham, turkey, roast beef, salami, provolone cheese, lettuce, tomato, onion, and mayonnaise. The sandwich is often served cold, but can also be heated in an oven or on a griddle to melt the cheese and warm the meat. American subs are a popular food item in the United States, and can be found at delis, sandwich shops, and fast food restaurants across the country.