In “Performative Acts and Gender Constitution: An Essay in Phenomenology and Feminist Theory” Judith Butler follows up on her thought in publications such as "Gender Trouble", "Critically Queer" and "Bodies that Matter". Butler's agenda is that gender roles are assigned through the "performance" of socially sanctioned practices (from the way we dress to the way we move all the way to the way our social position is perceived). For Butler, one is not born a man or a woman, one simply acts as a man or a woman act. Gender, in other words, is constituted through performance and it is perfomativity that governs gender division.
This gender division is for Butler the result of a binary system that also bears within it power relations. In other words, roughly speaking, the female "performance" is of subordination to men. On the other hand, binary oppositions always have liminal spaces between them and this is where subversiveness can come into play (see also Butler's "Subversive Bodily Acts"). Since gender identity is the result of social construction (or constitution in Butler's words) mediated through acts, it follows that acts can also serve to challenge these social constructions. Social expectations and taboos confine the acts that we perform ("you can't dress a baby boy pink and a baby girl blue"), but these can also be challenged thus undercutting these constricting social norms. This makes performance in Butler's eyes not just a site for gender oppression but also a potential form gender resistance an liberation.
Somewhat similar to Erwing Goffman's The Presentation of Self in Everyday Life, Butler sees to social arena as a theatrical stage on which we all play our assigned roles. Much like Foucault's concept of Discourse in writings like "The Subject and Power", Butler sees our gender roles as part of a discursive array through which power relations operate. To be sure, Butler therefore rejects any existentialist "natural" view of gender. Butler's essential point in "“Performative Acts and Gender Constitution" is that acts assigned with gender significance (like wearing make-up, for example) should not be treated as "natural" and that a careful critical scrutiny of them can go a long political way for gender equality and liberation.
Additional books by Butler to check out: