All people belong to social groups. We differentiate, for example, between higher and lower classes, between highly and low-skilled individuals, or between men and women. Belonging to social groups is often associated with social inequalities. Understanding what social inequality means and the explanations for it is the topic of this reader. It gathers key theoretical texts on social structure analysis that every student of social sciences should read during their studies. Following the introduction, which presents the most important basic concepts, there is a compilation of classical theories on social inequality, such as those by Kingsley/Moore, Marx, Weber, and Bourdieu. This is followed by texts from Dahrendorf, Schelsky, and Beck that trace the debates surrounding class and strata. Contributions on more recent theories and L. follow.