In Germany the first part of the plate indicates the city (Wü=Würzburg, or e.g. M=Munich, B=Berlin, F=Frankfurt etc.).
The major cities have 1 letter, medium-size cities have 2 letters, small urban areas 3.
The rest is a combination of letters and numbers, similar to the US.
The stickers - aside the city code - indicate the technical inspection date (rear plate) and the emission control date (front plate).
As long as You stay in the same city You can keep the plates from one car to the other.
When You move to another city You need new plates and - invalidating/ removing the 2 stickers from the old ones - You can also keep them as a "souvenir".
I still have mine infact...