Bolshevism is the name given to a socialist communist ideology that was European, rather than just a Russian doctrine. Bolsheviki, the correct plural of Bolshevik, means "of the majority".
They were the Marxist members of a wing of the Russian Social-Democratic Workers’ Party, which, led by Lenin, seized control of the government in Russia in October 1917.
The Bolsheviki became the dominant political power in Russia and set the political tone that has largely remained to this day, although undermined by recent access to the West and the peoples' realisation that a more comfortable if less worthy life lies outside of communism.