How did Karl Marx distinguish the bourgeoisie from the proletariat?

In Marxist theory, Karl Marx distinguished the bourgeoisie from the proletariat primarily through their relationship to the means of production.21

• The Bourgeoisie: This class consists of the owners of the means of production—such as factories, tools, and raw materials—within a capitalist system. Marx credited this class with a "heroic" role in modernizing society and revolutionizing industry, though he argued they seek to monopolize these benefits by exploiting the labor of others.2134
• The Proletariat: Often referred to as the working class, this group is defined as propertyless. Because they do not own the means of production, they are forced to sell their labor to the bourgeoisie to survive. Marx described the worker in this system as becoming a mere "appendage of the machine," effectively losing their independence.341

Marx viewed the conflict between these two classes as the central driver of social evolution and history, ultimately predicting that the exploitation of the proletariat would lead to a revolution that would abolish class distinctions entirely.321