Marxism is an intellectual school of thought that traces its origins to its eponymous founder, Marx, and continues in several forms today. One of the most expansive traditions of Marxist thought applies to cultural studies.
A fundamental proposition of Marx's, found in the Communist Manifesto, is that all of human history has been composed of class struggles. Early readers of Marx's work took class divisions as existing fundamentally on the economic level, and so took any study of human interaction - e.g., politics or history - as reducible to a study of the economic conditions which produced these events, a reductionist view called economism. Later opponents of Marxism caricatured all Marxist thought as economist, implying that economism provided too simplistic an understanding of the relationship between economic conditions and politics, society, or culture.
Marxist scholars such as Althusser have attempted to re-read Marx as providing a more robust and complex theory than economism. To this end, they introduce the notion of overdetermination, whereby multiple factors - not just the economic one - determine the structure of society. Althusser complicates Marxism in this way by identifying several distinct factors that structure society. He first extrapolates the idea of reproducing the means of production - originally found in Marx's Capital - to apply not only to the physical components of labor but also an ideology that perpetuates the current class and economic system. Secondly, Althusser further separates the structure of society into two components, base and superstructure, and focuses on how the latter, with institutions such as churches, schools, and bureaucracies, maintains the ideology that allows for the reproduction of the means of production in the base.
Another scholar, Stuart Hall, has noted additional cultural determining factors that Marx overlooked, including gender, race, and ethnicity.
Benedict Anderson has contributed to the expansion of Marxist study with the introduction of the idea that nationalism is a vital factor in societal development and must be reconciled with or incorporated into Marxist study. Anderson's explanation of print capitalism in particular, may be useful to understanding the origins of nation-state society.
Other information on Marxism may be found by following this interwiki link.