The document discusses social differences and social stratification. It notes that sociologists study differences in terms of inequality, stratification, and class. Inequality refers to unequal access to social rewards, stratification refers to how inequalities are passed down through generations, and class refers to social groups with unequal access to wealth, power, and prestige. The document then examines different systems of social stratification including slavery, castes, estates, and social class. It discusses Karl Marx's theory of class struggle and exploitation as well as Max Weber's focus on class, status, and power. Finally, it defines social mobility as movement within a stratification system and describes different types.