According to Encyclopedia Britannica, the Iron Curtain separated the Soviet Union and its eastern and central European allies from the West. The phrase "iron curtain" had been used since the 19th century as a metaphor, which gained widespread significance when used in a 1946 Winston Churchill speech.
The Iron Curtain was, unlike the Berlin Wall, not as much a physical barrier as an ideological, military and political barrier. The Soviet Union erected the barrier after World War II in order to prevent open contact with Western, non-communist influences. The communists abandoned one-party rule in Eastern Europe in 1989-90, dramatically reducing, if not entirely erasing, the significance of the Iron Curtain.