It is criticizing a legal decision where a judge found that a company that had fired all of the black women working there had not discriminated against them on the basis of their race, because it had not fired black men, nor on the basis of their sex, because it had not fired white women. Thus the judge decided that their civil rights had not been violated, and used the word "intersection" in the formal decision, that's why Crenshaw chose it.

She then extrapolates into some other situations where people are afforded less protection due to being at an "intersection" of legal categories in this way. But the way people use "intersectional" now, either in support or against, is almost completely different from what was originally meant and in fact is often exactly what she wrote the paper in criticism of.

> This is even more true today, when the intersectional grid draws rigid lines between “oppressor” and “oppressed” that Baldwin, despite the animus against white America that ballooned as he aged, was far too subtle a thinker to accept.

If you think that the inline definition of "intersectional" is an accurate one, the rest of the essay follows. You may or may not learn anything, though if this prompts you to read "Go Tell It on the Mountain", that would be a great outcome.

If you actually know anything about theory, then you'll see the rest of the essay as rhetorical shadow-boxing with something no one is actually saying.