Sandberg is not shy about labeling herself or Lean In as feminist in approach, and her stated goal in writing the book is to combat gender inequality. That said, sexism is a complex and widespread phenomenon, and Sandberg does not attempt to address it in all its forms. Instead, she opts to focus largely on one particular problem—the relative absence of women in leadership positions—in the hopes that solving that imbalance will have a ripple effect on the rest of society. She further narrows her focus by spending less time on the structural or economic factors that keep women out of power (e.g., the wage gap) and more time on the social and psychological ones—most notably, stereotypes about gender and gender roles that affect both how women are perceived and how they perceive themselves. The latter, in particular, are the "internal barriers" to success that Sandberg hopes her book can help address (8).

Over the course of Lean In, Sandberg identifies several gender norms that conspire to hold women in the workforce back—for instance, the expectation that women be passive and agreeable, or the association between femininity and nurturing behavior. The majority of these stereotypes arise from a broader notion of "separate spheres"—an ideology that took root in Western society over the course of the 18th and 19th centuries, assigning each gender to a "sphere" of life and allocating character traits accordingly.