The Bolsheviks were one of the parties in the Russian Social Democratic Labor Party (the Communist Party)
The RSDLP (from which the Bolsheviks eventually split from) was a group of social and political reformers that believed in Karl Marx’s philosophy.
The important parts of Marx’s theory as it applied to the Bolsheviks were that:
1) Confict theory – Marx believed that history was formed by the conflict of classes (hunter/gatherers versus agriculturalists, serfs versus lords, capitalists versus socialists, etc.), and that any meaningful social change could only be brought about through conflict.
2) Labor theory of value – In Marx’s economics, a good is only as valuable as the labor put into it, and that capitalists (the people who hold the means of production: capital, land, the tools to work, etc.) do not pay laborers the full value of their work, so the relationship between capitalist and laborer is inherently unequal
3) History – Marx viewed history as an evolution of social systems. Primitive society were the hunter-gatherers and early agriculturalists, who were replaced by feudal society, then by capitalism, and that capitalism will be replaced by communism.