"Gender" is sex roles and sex-role stereotypes. That is it. There is nothing else to add.

There are ONLY two "genders" or groups of sex roles. There aren't fifty or one hundred or twenty--ONLY two groups: masculinity and femininity. That is because there are only two sexes. Those "genders," a term I hate and use sex roles instead, which was the original phrase, are supposed to be complementary to each sex. They are a hierarchy, so the personality traits men don't like or the work men are too lazy to do or think they are too good to do, they force on women. It is as simple as that. We don't need to overthink it.