Answer by taking a quote from the following article:

Judith Butler FBA (born February 24, 1956) is an American philosopher and gender theorist whose work has influenced political philosophy, ethics and the fields of third-wave feminist, queer and literary theory. Since 1993, she has taught at the University of California, Berkeley, where she is now Maxine Elliot Professor in the Department of Comparative Literature and the Program of Critical Theory. She is also the Hannah Arendt Chair at the European Graduate School. Butler is best known for her books Gender Trouble:

In this essay, Judith Butler proposes her theory of gender performativity, which would be later taken up in 1990 throughout her work, Gender Trouble. She begins by basing her theory of gender performativity on a feminist phenomenological point of view. She suggests that both phenomenology and feminism ground their theories in "lived experience". Further, in comparing phenomenologist Maurice Merleau-Ponty and feminist Simone de Beauvoir, Butler argues that both theories view the sexual body as a historical idea or situation; she accepts this notion of a "distinction between sex, as biological facticity, and gender, as the cultural interpretation or signification of that facticity". This combination of theories is essential for founding Butler's view of "theatrical" or performative genders in society.  Butler argues that it is more valid to perceive gender as a performance in which an individual agent acts. The performative element of her theory suggests a social audience. For Butler, the "script" of gender performance is effortlessly transmitted generation to generation in the form of socially established "meanings": She states, "gender is not a radical choice... [nor is it] imposed or inscribed upon the individual". Given the social nature of human beings, most actions are witnessed, reproduced, and internalized and thus take on a performative or theatric quality. With Butler's theory, gender is essentially a performative repetition of acts associated with the male or female. Currently, the actions appropriate for men and women have been transmitted to produce a social atmosphere that both maintains and legitimizes a seemingly natural gender binary. Consistently with her acceptance of the body as a historical idea, she suggests that our concept of gender is seen as natural or innate because the body "becomes its gender through a series of acts which are renewed, revised, and consolidated through time".  Butler argues that the performance of gender itself creates gender. Additionally, she compares the performativity of gender to the performance of the theater. She brings many similarities, including the idea of each individual functioning as an actor of their gender. However, she also brings into light a critical difference between gender performance in reality and theater performances. She explains how the theater is much less threatening and does not produce the same fear that gender performances often encounter because of the fact that there is a clear distinction from reality within the theater.  Butler uses Sigmund Freud's notion of how a person's identity is modeled in terms of the normal. She revises Freud's notion of this concept's applicability to lesbianism, where Freud says that lesbians are modeling their behavior on men, the perceived normal or ideal. She instead says that all gender works in this way of performativity and a representing of an internalized notion of gender norms.

What were the Performative Acts?
Butler argues that it is more valid to perceive gender as a performance in which an individual agent acts. The performative element of her theory suggests a social audience.