In this essay, Deborah Tannen is arguing that women are judged by society based on their looks and their fashion choices in a way that men never are. She argues that everything that women do in terms of picking clothing, hairstyles, make up, etc. is "marked."
Tannen says that some words and actions are "marked." That is, they have certain connotations that make us think in various ways. A woman who does not wear makeup, for example, is "marked" as someone who is (in some people's eyes) less feminine. A woman who chooses to wear certain kinds of makeup and clothing might be taken less seriously because those choices are "marked" as sexy and unprofessional.
Tannen argues in this essay that all choices that women make with regard to their looks are "marked" whereas most choices that men make are not.