[mellonxcollie]

Disclaimer: I am not trans. Just feminist trying to explain as best I can

Back in the day people considered gender to be a binary thing. You were either male or female, and this gender was based on your biological sex characteristics. Nowadays people realize that gender isn't binary, it's a spectrum, and people can land on the spectrum pretty much anywhere.

Gender identity is realizing for yourself where you, personally, fit into the gender spectrum of society. The spectrum itself is a construct but your gender identity is something you find for yourself, about where you fit into that construct personally.

A lot of people consider themselves to be "non-binary" people. and this just means they either don't believe in the gender binary/societal constructs, or they believe they do not have a place within them and they do not fit society's traditional male/female constructs.