Gynesexual or gynosexual, previously also known as femsexual, is a term with several possible definitions.
First, is the exclusive attraction to women. This means that heterosexual men, lesbian women, and non-binary individuals attracted to women can be considered gynesexuals. Another word for this definition is womasexual.
Thirdly, is the attraction to "female anatomy" regardless of whether that individual identifies as female, however this definition is sometimes considered transphobic, as it reduces individuals to their genitals.
This identity is sometimes referred to as "gynephilia" or "gynophilia," however those terms are outdated. Previously the term was used interchangeably with femsexual, however they have diverged enough that they are now typically considered separate terms.
The term was possibly made with non-binary or genderqueer individuals in mind. However, many non-binary individuals prefer terms like finsexual, venusic, or womasexual to describe this attraction, because gynesexual has no agreed upon definition, which can make it's usage confusing, and it can have unfavorable connotations. The term gnyesexual is commonly used by transphobes as a reason to exclude trans women because they are only attracted to "female anatomy" or "real women". Under this definition, it reduces individuals to their genitalia, putting cis women and pre-surgery trans men in the same group because they have "female anatomy". The prefix gyne- means "woman" or "female," which may imply that one sees "female anatomy" and being a woman as interchangeable.
The pink was taken from the trans flag to symbolize attraction to women. It is also presumably to show that trans women are real women. The brown represents stability and support. The green was taken from the genderqueer flag, it symbolizes attraction to femininity and also implies that this term was made for genderqueer/nonbinary individuals. It is uncertain the origin of this flag.