A submarine sandwich, often called a sub, is a type of sandwich made with a long roll of bread, typically filled with various ingredients. Common fillings include meats like turkey, ham, or salami, along with cheeses, vegetables, and condiments. The bread is usually soft and can be toasted or served cold. Submarine sandwiches are popular in many regions, especially in the United States, where they are often associated with delis and sandwich shops. They can be customized to suit individual tastes, making them a versatile meal option for lunch or dinner.