Meaning "minority" in Russian, the party was formed in 1903 from a split in the Russian Social Democratic Labour Party (R.S.D.L.P), which created the Bolsheviks and Mensheviks parties.
During the 1905-07 revolution the Mensheviks opposed the working class and peasantry who were in open revolt. They believed that Socialism should only be achieved firstly through a bourgeois revolution (via reformism); following this revolution, they felt the working class and peasantry would then be able to revolt against the bourgeois, and establish Socialism.
After the successful bourgeois revolution of February 1917, most Mensheviks joined the provisional government, though as a party they had no power. After the October Revolution the Mensheviks opposed the Soviet government, primarily through bureaucratic lobbying, though some members later joined the white armies.
Encyclopaedia of Marxism