The Soviets following WWII in the 1950s- 1960s invaded Eastern Europe to form The Iron Curtain. The goal was to create a buffer and communist puppet governments were set up.
Communism in Europe and Russia lasted until the early 1990s with the breakup of the Soviet Union. This was one of the last of the dominos to fall in Europe. The Soviet Union started to decline as the Eastern Bloc countries like Poland, Hungary and Czechoslovakia, Yugoslavia, Romania, East Germany, Bulgaria and Albania all deposed their communist leaders and started to be free.
Lech Walesa with Solidarity was one of the changes in Poland.
Erich Honnecker, President of the DDR. would be deposed as the Berlin Wall fell in November 1989 and followed by a German Reunification in October 1990.
Romania saw Ceaucsescu deposed, murdered and his brutality brought to light.
Czechoslovakia broke up into 2 separate countries. The Czech Republic and Slovakia.
Yugoslavia split and had a bloody civil war. Slobodan Milosevich committed holocaust- like crimes against Kosovar, Croatian and Bosnian Serbs who were Muslim.
Lastly, the Soviet fell with a failed military coup led by Gennady Yanayev to oust Gorbachev from power in August 1991 with the Soviet Union lasting until December 25, 1991. The communists wanted Gorbachev out because of the reforms of Glasnost (openess) policies and the Perestroika movement that loosened power over eastern Europe. Gorbachev was making The Soviet Union more democratic. The communist party had collapsed as a new Russian Federation called the Commonwealth of Independent States was formed. It would be led by Boris Yeltsin who was the president of the Russian SFSR. Ukraine and the Baltic States (Latvia, Estonia and Lithuania became independent countries. The economy itself began to have private ownership.
The other impact of the fall of the Soviet Union was in the proliferation of nuclear weapons. In the 1990s, it was a huge concern that countries like Iran and North Korea would try to get nuclear weapons.
Some of the former Eastern Bloc countries would formally join NATO. Among them, Poland and Hungary.