Sex and Gender
Gender refers to the socially built characteristics of women and men - namely norms, roles and relationships of and between groups of women and men. It varies among different cultural groups and can be modified.
Most people are born either male or female, and therefore raised with specific rules and behaviors, including how to interact with others of the same or opposite sex, and within the family, the community and the workplace.
When individuals or groups do not "adapt" to the established gender norms, they often become victims of stigma, discriminatory practices or social exclusion, and all these consequences negatively affect their health. It is important to be sensitive to the different identities that do not necessarily fall into the categories of "binary" sex, ie male or female.
Gender norms, roles and relationships influence people's susceptibility to different health conditions and illnesses and influence their ability to enjoy health state, and physical and mental well-being.
These rules, roles and relationships also have an impact on the access and assistance of health services and on the health outcomes that people experience during their lifetime.
From:
http://www.who.int/gender-equity-rights/understanding/gender-definition/en/