People often use the terms gender and sex interchangeably when talking about a person being male or female. However, the terms are very different and apply to different aspects of a person’s identity.
Sex refers to the biological differences between people (chromosomes, hormonal profiles, or internal and external sex organs).
Gender refers to cultural values that are either masculine or feminine, some combination of both, neither, or something else.
Gender identity refers to how one thinks of one’s own gender: whether one thinks of oneself as a man (masculine) or as a woman (feminine.) The way society expects a feminine or masculine person to act (dress, speak, relate to others) is called a gender role or social gender role and forms our construct or definition of what gender is.
Gender expression is how people might communicate their sex/gender to others: clothing, hair styles, mannerisms, way of speaking, roles we take in interactions, etc.