We act as if that being of a man or that being of a woman is actually an internal reality or something that is simply true about us, a fact about us, but actually it's a phenomenon that is being produced all the time and reproduced all the time, so to say gender is performative is to say that nobody really is a gender from the start.

[G]ender is culturally formed, but it's also a domain of agency or freedom and that it is most important to resist the violence that is imposed by ideal gender norms, especially against those who are gender different, who are nonconforming in their gender presentation.

-Judith Butler