The Union of Soviet Socialist Republics was a country in Europe and Asia. Throughout it's history, the USSR has been a very influential and powerful country.
The Soviet Union began in 1922 when Vladimir Lenin and the Bolsheviks overthrew the Russian Empire's government. Believing in the ways of Karl Marx, Vladimir Lenin introduced communism to the new country. This country was since then named the Union of Soviet Socialist Republics.
The Cold War was likely the most important part of USSR history. This war was an attempt to spread the influence of the USA and the USSR. Through threats of nuclear war, both sides tried to be the most influential country in the world. This war ended in 1991 when the Soviet Union fell.
The Soviet Union ended over a period of time from 1989 to 1991. In 1989, the Berlin Wall had been taken down, thus uniting the Federal Republic of Germany (West Germany) and the German Democratic Republic (East Germany). This was a symbol of the Iron Curtain being raised and ending the reign of the USSR. After that, many Soviet states had seceded from the USSR. By 1991, all the states had broken off and the USSR was declared a collapsed country.