(Also gynephilia, or gyne) In behavioral science it's the attraction to the woman
gender, rather than the female sex. This means they are capable of being attracted to someone if their gender identity is a woman. This includes both trans women, and cis women.
People of any
gender, or sex can be gynesexual. Which means straight
men can be gynesexual, as well as lesbians, and non-binary
people.
Along with gynesexual, androsexual is the attraction to the man gender. Ambisexual includes both gynesexuality, and androsexuality.
This shouldn't be confused with femmesexual / femsexual, which is the attraction to the feminine gender expression, rather than the woman gender identity. However someone can be both gynesexual, and femmesexual.