Allgender bathrooms?

Why do they say "allgender" suddenly?

As we learned in 3rd grade there are two genders. Xx chromosome is the girl and xy chromosome is a boy.

Does anyone know why this now is called allgender?

Pls help, I'm really confused about this new development
Updates
+1 y
Thanks for all the help in explaining this. Thanks to both Boys and girls / men and women for educating me. It was interesting but also a little crazy to see some of you say that human beings (xx chromosome =girl / xy = boy) say there's a third gender. I'm guessing gays are considered a gender nowadays, which is silly lol, but it's ok
Allgender bathrooms?
Post Opinion