The word "heterosexual" refers to an individual who is attracted to members of the opposite sex. In other words, it describes a sexual orientation where a person—be it a man or a woman—has romantic or sexual feelings towards people of the gender different from their own.
The term "heterosexual" is derived from the combination of the Greek prefix "hetero-" meaning "different" or "other," and the Latin root "sexualis," which pertains to sex. The term emerged in the late 19th century.