What was Judith Butler's argument regarding gender from a post-structuralist perspective?

Butler argues that although feminists rejected the idea that biology is destiny,many developed an understanding of patriarchal culture that positioned masculine and feminine genders as inevitable.Butler argues instead that there is no essential basis to gender,nor is there some authentic femininity or masculinity that is rooted in female or male bodies.Butler asserts that gender can be viewed as a performance: "there is no gender identity behind the expressions of gender....identity is performatively constituted by the very 'expressions' that are said to be its results."