This unofficial boundary is known as the Iron Curtain.
Winston Churchill expressed this concept of an Iron Curtain in a post World War II speech. In this speech he is referencing the imaginary border between the Soviet Union and their satellite nations, and the Western portion of Europe. This "iron curtain" symbolized the two different approaches to economic and government policies in Europe after World War II. The Western European countries were mostly capitalist while the countries under Soviet influence were mainly communist.
