[Germany] What is this portion in OSM adresses?

I am a regular Osmand user, but I don't know much about how OSM works in detail. I noticed that in some services that use OSM, addresses appear like in this screenshot.

This second part of the address often has interesting names that I've never heard even for places I know well.

To me it looks like the name of a Gemarkung or something similar.

• What's the correct term for this part of an address?
• Where is this data derived from?
• Is it possible to show a map with the borders of these Gemarkungen (or whatever it is called)?

Also glad if someone can point me to the docs where I can read about this. I browsed the wiki but couldn't find what I was looking for.

Also interested about the correct terms for the other parts of the addresses.

Thanks!