A hamburger, or simply a burger, is a dish consisting of fillings—usually a patty of ground meat, typically beef—placed inside a sliced bun or bread roll. The patties are often served with cheese, lettuce, tomato, onion, pickles, bacon or chilis with condiments such as ketchup, mustard, mayonnaise, relish or a "special sauce", often a variation of Thousand Island dressing and are frequently placed on sesame seed buns. A hamburger patty topped with cheese is called a cheeseburger. Under some definitions, a burger is considered a sandwich.
Hamburgers are typically associated with fast-food restaurants and diners, but are also sold at various other restaurants, including more expensive high end establishments. There are numerous international and regional variations of hamburger. Some of the largest multinational fast-food chains have a burger as one of their core products: McDonald's Big Mac and Burger King's Whopper have become global icons of American culture.