For those who are visiting a city for just a day on a trip, the question might right arise: what is one to do with one's luggage? Well, if one is arriving by Deutsche Bahn, many of the train stations in Germany offer lockers in various sizes where one can store luggage for a short time.
Even my own local main train station (Hauptbahnhof) in Kaiserslautern offers lockers. When entering the train station from the main entrance that faces downtown, go down the stairs and turn left. The lockers are located there and offer various sizes and rates; the largest lockers could accommodate most suitcases. The locker pictured below is 3 euros to rent. The time limit on use is 72 hours.
The German word for luggage is "Gepäck," pronounced something like "geh-peck." The word for suitcase is "Koffer."