Eastern Europe refers to the eastern part of Europe. It includes European part of Russia (40% of European continent), the Caucasus (Armenia, Azerbaijan and Georgia). the European part of Kazakhstan and often Belarus and Ukraine, though they are geographically Central European.
Cold War meaning
During the Cold War, eastern Europe was confused with the term Eastern Block, including the USSR (occupying eastern Europe, parts of northern Europe and Northern Asia), and after the World War II its allies in Central Europe (East Germany, Poland, Czechoslovakia (now the Czech Republic and Slovakia), Slovenia, Hungary), Baltic States (Estonia, Latvia, Lithuania) and the Balkans (Bulgaria, Romania, Moldova, Serbia, the rest of Former Yugoslavia).
A large part of eastern Europe is now democratic and has introduced market economies. Baltic countries (formerly occupied by the Soviet Union) - Estonia, Latvia, Lithuania -, Central Europe and some countries in the Balkans (Romania, Bulgaria) are now in the European Union.
Russia, Ukraine and Belarus hope to join the European Union later. Russian oligarchic democracy is holding onto control of Belarus, Ukraine and the Caucasus countries, affecting their democracies. Part of Russia is in eastern Europe (called European Russia). Russia is expected to join the EU in 2030, according to some liberal politicians. It is a common faux pas to use the terms either "eastern Europe" or "Eastern Europe", since it refers to European Cold war, is often confused with the Eastern Bloc, and Russia (its European part) occupies 40% of Europe's landmass, leaving little room for other European regions.
Countries of Eastern Europe
The countries of eastern Europe always tend to include: