At its most basic definition, the term “Eastern Europe” refers to the eastern half of that continent. However, for most people, when conceptualizing Eastern Europe, the term refers to those countries that fell under the influence of the Soviet Union during the Cold War.
Geographically, Europe’s eastern most edge is comprised of the Ural Mountains, the Ural River, and the Caucasus Mountain range, all of which are in Russia. Following the end of World War II, the Soviet Union established a number of communist puppet regimes in order to provide a barrier between itself and the democratic nations of Western Europe.
Under a Cold War definition, the countries of Eastern Europe included the Soviet Union, Poland, East Germany, Hungary, Czechoslovakia, Bulgaria, and Romania. With the collapse of the USSR, the independent nations that were former Soviet republics, including Ukraine, Belarus, Moldova, the Caucasus nations of Georgia, Armenia, and Azerbaijan, and the Baltic nations of Latvia, Lithuania, and Estonia can be said to comprise Eastern Europe in addition to former communist nations, although East Germany reunified with West Germany, and Czechoslovakia split into the Czech Republic and Slovakia.