Class conflict also referred to as Class Antagonism, Class Warfare and Class Struggle is a very significant concept from Marxist theory which speaks of the socioeconomic contradiction between the working class and capitalists. Capitalist or Bourgeoisie is the one who owns means of production as private property, like a factory, mill or an industry et cetera and Proletariat or worker is one who sells their labour to Capitalist for wages in return and is consequently alienated from the very aspects of humanity.
It's clear that a capitalist always makes more from the labour of the worker than what the worker gets paid, that's how capitalist exploitation works, So, what he extracts from the worker's labour is known as Surplus Value.
Such economic competition and contradiction among social classes; ie. proletariat and bourgeoisie- causes Class Warfare which can be observed in forms of Direct Violence and Indirect Violence.
Direct Violence includes revolution, assassination, wars for resources and cheap labour while Indirect Violence includes deaths from unaffordable healthcare, unsafe working conditions, starvation, and the threat of unemployment.
"History of all hitherto existing societies is the history of class struggles," said Karl Marx in Communist Manifesto.
'The best way to define slavery is by quoting Mikhail Bakunin a libertarian socialist.
"Slavery may change its form or its name- its essence remains the same. Its essence may be expressed in these words: to be slave is to be forced to work for someone else, just as to be master is to live on someone else's work."
Let's examine how this Theory of Class Conflict can help us develop a revolutionary and dialectical understanding of History and analyze how Slavery has been changing its names and forms but in essence/function, has always remained the same.
Dialectically identity of material reality lies in its function, not the form.
The theory of Class Conflict is used to break away from false consciousness and capitalist hegemony which commodifies humans and holds capital above everything else.
Here's a simple example where we have analyzed Class Conflict throughout history.
Forced by the Master's whip to polish his shoes, clean his house, wash his clothes, cook food for him, and work for him, in the fields, or in the trade market. Simply serving him and working to make him wealthier was a slave's job and in return Master provided for his basic needs to survive.
Forced by Baron to polish his shoes, clean his house, wash his clothes, cook for him, work for him in fields and simply work to make him wealthier was Serf's job and in return Baron provided him but mostly not enough to even meet basic needs to survive.
Forced by hunger, the instinct to survival, Economic Coercion & Circumstantial Coercion to polish his shoes, clean the house, wash his clothes, cook for him and work in mills, industries, and factories to make him wealthier. Serve him and work for him to make him wealthier while in return the wage slave gets a wage so small that it's hard to meet the basic needs of life to survive. Many die out of starvation and unaffordable healthcare.