The term "agency" suggests that we have control over the course of our lives. However, as many modern sociologists have observed, much of our lives are socially determined by the structure of the environment in which we operate. Individuals such as Nietzsche, Sartre, Althusser, and Foucault criticize the notion that morality, or knowledge of right and wrong, are predetermined by the society in which individuals live. Choosing to follow the conventions of our respective societies would seem to suggest that humans have no authentic agency. Instead, we are brainwashed or indoctrinated into believing that certain actions are appropriate while others or not, and we blindly act upon them. By this logic, the only way to assert agency is to deviate from those socially prescribed norms.
In these kinds of arguments, structures of society and agency are diametrically opposed. Bourdieu, on the other hand, introduces the notion of habitus to reconcile the two. He suggests that individuals operate within a "field," or a particular social environment, and become habituated to the norms and actions that occur within that field. Imagine, for instance, a young child in school (which is a specific field). The child knows to hang up her coat when she walks into the classroom, to go to her desk, and raise her hand when she has a question. She is not fully conscious of these actions; instead, they become second nature to the student. She is also a part of other fields, and thus, she also has rules at home, rules within her friend groups, and certain rules with any other activities or groups to which she may belong. She learns these rules just as she has learned the rules in school. When all of these different rules come together and form various habits for her, they form her habitus. Given all of her experiences, her habitus is unique--no one person belongs to all of the same groups just as she does, and no one person has embodied the rules of said groups in exactly the same way. This makes for a unique individual. Further, these rules do not simply exist to be picked and chosen at will, resisted when they are no longer convenient. These rules, instead, become a part of this student; they are inscribed upon her. So, when she makes an action based upon her habitus (the unique amalgamation of rules associated with all of her interactions), she is acting with agency. Her actions externalize her habitus, and the world around her will react to her actions, providing her more information to base future decisions on. In this way, there is a constant feedback loop between agency, or the actions undertaken based on one's habitus, and the structure of the surrounding world.