In the context of history and culture, and especially in the context of women's history and the roles men and women have had in history, "sex" has come to refer to biological characteristics of men and women, and "gender" has come to refer to culturally-ascribed or prescribed characteristics of men and women.
Thus, "gender history" refers to the history of the roles of men and women -- how culture and society have seen certain behaviors as "proper" or "aberrant" for men or for women.
