The Menshevik Party was a faction of the Russian Social Democratic Labor Party. The Mensheviks were moderate socialists who advocated for a gradual transition to socialism through democratic means. They opposed the Bolsheviks, who believed in a more radical and immediate seizure of power by the proletariat.
“For instance, when, in the revolution of 1917, the question of the significance and role of the state arose in all its magnitude as a practical question demanding immediate action, and, moreover, action on a mass scale, all the Social-Revolutionaries and Mensheviks descended at once to the petty-bourgeois theory that the “state” “reconciles” classes. Innumerable resolutions and articles by politicians of both these parties are thoroughly saturated with this petty-bourgeois and philistine “reconciliation” theory. That the state is an organ of the rule of a definite class which cannot be reconciled with its antipode (the class opposite to it) is something the petty-bourgeois democrats will never be able to understand. Their attitude to the state is one of the most striking manifestations of the fact that our Socialist-Revolutionaries and Mensheviks are not socialists at all (a point that we Bolsheviks have always maintained), but petty-bourgeois democrats using near-socialist phraseology.” - The State and Revolution — Chapter 1: Class Society and the State
See RSDLP