Citizens United is two different but related things: a Political Action Committee (PAC) in Washington, D.C., and a Supreme Court case about election spending in which the aforementioned PAC was the plaintiff. Both lie at the center of a debate over the role corporations should play in society.
There’s a misconception spreading that Citizens United is an extension of corporate personhood. It’s not. While it’s true that Citizens United strengthened 1st amendment protections for corporations, the basis for that protection isn’t personhood. Rather, the court’s decision rests on something else.