The description of intersectionality arose from a need to articulate that Black women in America were experiencing unique forms of discrimination that were related not only to their race, nor only to their gender, but to both of those aspects of their humanity simultaneously.
As one understands this reality, it becomes clear how it can apply to the experiences of multiple forms of discrimination or injustice. For example, a person who is disabled and wealthy will face fewer struggles than someone who is disabled and poor. Certain aspects of their experience will be very similar, but it is easy to understand that a person's experience of the world is impacted by aspects of their intersectional identity.
Intersectionality is a term coined by legal scholar Kimberle Crenshaw in 1989. She introduced it as a way to discuss the complex and cumulative way that the effects of different forms of discrimination (such as racism, sexism, and classism) combine, overlap, and intersect - especially in the experiences of marginalized people or groups.