Hamburger

A hamburger is typically considered to be a variant on a sandwich involving hot meat, though rarely using actual "ham". The name is a shortened form of "Hamburger steak", named after the German city of Hamburg.

Two independent definitions of what differentiates a "burger" from a "sandwhich"

1. Burgers use processed meat, regardless of the type of bread.
2. Burgers use a "burger" bun, regardless of the filling.

The McDonalds BigMac is possibly the most famous hamburger. Almost certainly the worlds biggest selling.

Ingredients for a burger vary. Traditional US burgers seem to contain simply meat and cheese. Australian hamburgers have tomato, lettuce, cheese and meat (with BBQ or tomato sauce) as minimum, and can be optioned to include beetroot, onion, egg, bacon, and pineapple. (aka "burger with the lot")