Why do hamburgers use open buns?

When we go to a fast food restaurant to order a burger, the waiter will bring us a bun. This bun is cut and there will be a layer of meat in the middle, such as beef, There is pork, and a little lettuce is put on the patty, and then their homemade sauce is put in, so it is a burger, so what exactly is a burger? In layman's terms, it's just meat sandwiched between bread

Why do we call this kind of food a hamburger?

Some people say that the name comes from Hamburg, the second largest city in Germany. Some people say that it comes from a food called hamburger steak (a patty made of minced beef). Some people say that it comes from Hamburg. On hamburgers.

Are these claims credible? The Library of Congress in the United States officially states that the first hamburger was sold in 1900 by Danish immigrant Louis Larsen from his food truck. But so far, many people have objected to this claim, and before that, many people have come up with evidence of their own invention of the hamburger.

For a long time, we didn’t know who invented this burger, because the same sandwich made of lettuce and bacon sandwiched between bread had appeared in the United States earlier. The real name of Hamburg is actually related to the Port of Hamburg, which is also the reason why it is really named Hamburg.