A cheesesteak is a sandwich made in Philadelphia. It is made of a long hoagie roll, cut in half and filled with thin slices of steak and covered with melted cheese. The cheese is either provolone or cheddar in the form of whiz. Some cheesesteaks also have onions or green peppers. Pat's King of Steaks and Geno's are two famous places in Philadelphia that make cheesesteaks. Pat's is thought to be the place that popularized the cheesesteak.