Gender, as generally discussed within acedemic studies, is essentially the segregation of characteristics and behaviors that are associated with a particular sexual dimorphism. What these characteristics and behaviors are are culturally constructed signifiers that signal that sexual dimorphism that develop over time and are more or less arbitrary. However, their meaning is derived from the experience of gender by gendered individuals and the performance of gender. Essentially, if your sex is male, but you wish to identify as female, the best way to do so is to adopt the generally agreed upon characteristics of a woman. But TreadOnMe, you ask, aren't those just stereotypes? Pretty much, yeah. But gender is real in the same way all cultural practices are real, because society as a whole accepts it as such. Variation is allowed, but only within certain margins in certain areas of society.

However, gender is particularly weird in the west because of the amount of outrage variation causes. A Hollywood actor doing a facelift in order to be perceived as younger is odd but perfectly acceptable, but someone gets top surgery and people start losing their shit. I think it has something to do with Christian sexual pathology and conservative Western civilization collapse narratives, but that isn't something I'd really like to study.