The terms sex, gender and sexual orientation are often used interchangeably. Despite sounding similar, they actually have three distinct meanings.
Sex: Biological maleness or femaleness. Males have XY chromosomes. Females have XX chromosomes. Sex is determined the instant a woman's egg is fertilized by a man's sperm. If an X sperm fertilizes an X egg, the fetus will be female. If a Y sperm fertilizes the X egg, the fetus will be male.
Gender: The behavioral, cultural, and psychological traits typically associated with one sex. Babies are usually assigned a male gender at birth if they have a penis, and a female gender if they have a vulva. Gender identity is how someone feels about their gender assignment
Sexual orientation: Who someone is attracted to romantically and sexually.