The document discusses sex and gender. It defines sex as the biological differences between males and females determined at birth, such as reproductive organs and ability to bear children, which do not change. Gender is defined as the social and cultural roles, behaviors, and attributes placed on males and females in a society, which can change over time and vary between cultures. The document provides examples of sex characteristics like menstruation and voice changes during puberty. Gender roles and expectations like career choices, household duties, and parenting roles are influenced by societal and cultural norms. The document outlines how gender influences health across the lifecycle from birth through adulthood and old age due to both biological and social factors.