The term "Bolshevik" refers to a faction of the Russian Social Democratic Labour Party that emerged in the early 20th century. Led by Vladimir Lenin, the Bolsheviks advocated for a radical approach to socialism, emphasizing the need for a vanguard party to lead the working class in overthrowing the Tsarist regime. They believed in the necessity of a revolution to establish a socialist state. In 1917, the Bolsheviks played a crucial role in the October Revolution, which resulted in the overthrow of the provisional government and the establishment of a communist government in Russia. Their ideology and actions significantly shaped the course of the 20th century, leading to the formation of the Soviet Union.