Easy, simple and very clear, this explanation of social inequality from this article “Growing inequalities in science“.

One of the most common misconceptions regarding inequality consists of thinking that an unequal distribution of resources is the result of an unequal effort to achieve them. Although this might be the case in certain situations, when it comes to particular individuals, the fact is that there are systemic structural forces governing the result of our efforts. The possibility of our personal, social or professional success still pretty much depends on our ascribed status, that is, an involuntary assigned position within the society. Sociologists use the expression social stratification to describe the way in which these structural forces organize groups and individuals in a phenomenon common to all societies.