Question

What does the “iron curtain” refer to? Is it [the border between the Soviet satellite states and Western Europe]?

Answer 1

Iron curtain is the symbolism of the political, military and ideological separation of the Soviet satellite states and Western Europe including those areas where the World War II ended.. This was mentioned by the speech of Winston Churchill. This started the Cold war

Answer 2

Yes, the "iron curtain" indeed refers to the imaginary boundary dividing Europe into two separate areas from the end of WWII in 1945 until the end of the Cold War in 1991. These two separate areas are Soviet Union and its satellite states from Western Europe.