The German Democratic Republic (GDR) (aka East Germany) was a state in the Eastern Bloc during the Cold War period. From 1949 to 1990, it administered the region of Germany that was occupied by Soviet forces at the end of World War II—the Soviet Occupation Zone of the Potsdam Agreement.
The Soviet zone surrounded West Berlin, but did not include it; as a result, West Berlin remained outside the jurisdiction of the GDR. The Berlin Wall was first built in August 1961.
Definition adapted from Wikipedia, August 22, 2016.