A cheeseburger is a hamburger

Hamburger

A hamburger is a sandwich consisting of a cooked patty of ground meat usually placed inside a sliced bread roll...

 with 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....

 that has been added to it. Traditionally, the cheese is placed on top of the patty

Patty

A patty is a flattened cake, often of meat.Patty may also refer to:* Patty , a family name* Patricia, a female given name, in all forms of English* Patrick , a male given name, in Australian English and Hiberno-English...

, but the burger can include many variations in structure, ingredients, and composition. The term itself is a portmanteau of the words "cheese" and "hamburger." The cheese is usually sliced, and then added to the cooking hamburger patty shortly before the patty is completely cooked which allows the cheese to melt.