Deutsche Reichsbahn-Gesellschaft was an organization that existed a long time ago in Germany. It was responsible for running the train system in the country. Think of it like a big company that made sure trains ran smoothly and people could get to where they needed to go.
Before World War II, the group was controlled by the government and played an important role in helping with the war effort. After the war ended, the group was divided up and taken control of by different countries.
Today, the German train system is still very important and is run by a new organization called Deutsche Bahn. They have lots of different types of trains that go all over the country and even into other countries nearby!