Bolsheviks: A faction of the Marxist Russian Social Democratic Labour Party which split apart from the Menshevik faction at its Second Party Congress in 1903. The Bolsheviks seized power in Russia during the October Revolution phase of the Russian Revolution in 1917.
Vladimir Lenin: A revolutionary thinker and politician who played a pivotal role in history as leader of Russia from 1917 until his death in 1924. He was instrumental in turning Russia into a socialist state governed by one party - Communist Party.
Soviet Union: A federal socialist state that existed from 1922 to 1991. It was nominally a union of multiple national republics; but its government and economy were highly centralized.