A cheeseburger is a popular type of sandwich that consists of a cooked beef patty placed inside a sliced bun. The defining feature of a cheeseburger is the addition of cheese, typically melted on top of the patty. Common types of cheese used include American cheese, cheddar, and Swiss cheese. Cheeseburgers are often garnished with various toppings such as lettuce, tomato, pickles, onions, and condiments like ketchup and mustard. Cheeseburgers are widely enjoyed in many countries and are a staple in fast food restaurants and diners. They can be customized in numerous ways, allowing for a variety of flavors and styles. Some variations include the veggie burger for those seeking a meatless option or gourmet versions that feature unique ingredients.