Hegemony: the dominance of one group over another through force or ideology. The means through which one group calls “all the shots” in terms of both Material/Economic relations and beliefs.
Force is control of the body through the use or threat of physical coercion. Ideology is the control of the mind through the control of knowledge ("propaganda") or culture (belief).
Ideology: The control of knowledge to maintain existing or establish social class structures. A belief system adopted as “inherently true” that operates unconsciously and permeates a culture as truth itself. Dominant ideologies:
a) Appear neutral while those threatening existing class structure are painted as “radical” (ie: feminism)
b) Are “existential”: created by material conditions and relationships; thus the essence of belief follows existence, historical reality or “facts on the ground”. (people create the beliefs, rather than belief being an accurate understanding of "reality")
c) Explain material conditions of class structures (who is who’s ho); cultural beliefs, assumptions, taboos etc exist to keep the powerful (those who get rich from the system -- the Bourgeois) in power over those who are exploited by the system (the Proletariat).
There are many different types of Ideology. Remember, though, each justifies or challenges existing or new class relations and the relationship of people to the means of production. In traditional Marxist theory, dominant Ideologies exist to justify Bourgeoisie Hegemony: keeping "the man" in power and the worker exploited.