Okay kiddo, Landsmannschaft Ostpreußen is a group of people who used to live in a place called Ostpreußen which is now a part of Russia. These people moved away from their home because of a war a long time ago, but they still want to remember where they came from and their culture. So, they created a club or a group where they can meet other people who also used to live there and they can keep their traditions alive. They talk about their old homes, sing songs, dance and eat tasty food. It is like a big family where everyone is happy to see each other and share their memories.