Short answers, pulled from the story.
The Iron Curtain was the political and physical boundary that divided Europe from the end of World War II in 1945 until the end of the Cold War in 1990 and 1991. It separated Soviet-aligned states in the east, formally allied in the Warsaw Pact in 1955, from many western nations that were NATO members.
The phrase is often attributed to Winston Churchill's speech on the 5th of March 1946 in Fulton, Missouri, but Queen Elisabeth of Belgium used it in 1914 to describe a barrier between her people and Germany. Vasily Rozanov applied it to Soviet Russia in his 1918 work The Apocalypse of Our Time.
At Westminster College in Fulton, Missouri, on the 5th of March 1946, Churchill said that from Stettin in the Baltic to Trieste in the Adriatic, an iron curtain has descended across the Continent. He named Warsaw, Berlin, Prague, Vienna, Budapest, Belgrade, Bucharest and Sofia as cities now under Soviet control from Moscow.
East of the Iron Curtain were the three Baltic states of Estonia, Latvia, and Lithuania, along with Poland, East Germany, Czechoslovakia, Hungary, Romania, Bulgaria, Albania, and the USSR. The Red Army had invaded and annexed the Baltic states in 1940 on Stalin's orders.
The Iron Curtain took shape as razor wire, fences, fortified walls, minefields, and watchtowers, with the inner German border among the most heavily militarised areas in the world. In Hungary a double barbed-wire fence stood 50 m from the border with land mines between the fences, and dog patrols watched around the clock, authorised to shoot escapees.
The fall began as Mikhail Gorbachev relaxed Soviet intervention and a wave of revolutions swept the Eastern Bloc in 1989, including the Pan-European Picnic on the 19th of August 1989 where more than 600 East Germans fled into Austria. East Germany reunited with West Germany on the 3rd of October 1990, the USSR dissolved in December 1991, and Czechoslovakia dissolved in 1992.
The European Green Belt is a chain of natural biotopes that formed because of decreased human activity along the Iron Curtain's heavily fortified border during the Cold War. A long-distance cycling route called the Iron Curtain Trail follows the former border for 6800 km from Finland to Greece.