Heterosexual people love people (sexually and romantically) of the opposite gender. A heterosexual man loves women. A heterosexual woman loves men. Another less formal word for heterosexual is straight.
Heterosexual is seen as different from homosexuality, bisexuality or asexuality. Most people describe themselves as heterosexual. Society is described by some people as 'heteronormative', which is a word that describes an attitude that homosexuality is not 'normal'.