Lots of other people have already replied, but I didn't see this explanation yet. The concept of intersectionality came from a court case, DeGraffenreid v. Gen

Lots of other people have already replied, but I didn't see this explanation yet. The concept of intersectionality came from a court case, DeGraffenreid v. General Motors, where this black woman was denied employment. She had noticed that the company was hiring very few black women and thought they were being biased against her when they refused to hire her despite her qualifications. The court checked the numbers and they found that GM was hiring a sufficient amount of black men to not be racist, and a sufficient amount of white women to not be sexist. So, despite actually not hiring black women, GM was let off the hook. If you've studied set theory, you probably know the concept of the intersection of two sets: basically the middle part of a venn diagram. The theory of intersectionality says basically, when people are biased against you in more than one way (in this case through sexism and racism) that the effects compound to create a situation where people like you are underrepresented in terms of opportunities, in a way that affirmative action failed to take into account.