This is the 775th most frequent German word.
hamburger
A person from Hamburg, Germany, or a sandwich consisting of a cooked ground meat patty, typically beef, in a bun.
In this sentence, 'Hamburger' refers to the food item that is well-known—a sandwich with a patty in a bun.
Ich habe einen Hamburger zum Mittag gegessen.
I ate a hamburger for lunch.
Here 'Hamburger' means the people who are from the city of Hamburg in Germany.
Hamburger lieben ihre Hafenstadt sehr.
People from Hamburg love their harbor city very much.
In this instance, 'Hamburger' is used as an adjective describing something that belongs to or originates from Hamburg, here relating to its music scene.