Nonbinary is an umbrella for gender identities that don't sit cleanly in "man" or "woman" — both at once, neither, something in between, or something the two-box system never had a word for.
Nonbinary (often shortened to enby, from saying the letters "NB" out loud) is less a single identity than a whole wing of the building. It's the umbrella for anyone whose gender doesn't fit neatly in "man" or "woman": people who feel like both at once, neither, something that shifts by the day, or a category the two-box system never had a word for. Some nonbinary people also call themselves trans; some don't. Both are right — the label describes a relationship to the binary, not a fixed uniform.
The tired takes write themselves, so let's clear them: nonbinary isn't a 2014 invention, a phase, or someone being difficult on purpose. Cultures across the world named genders beyond two long before English got around to it. It's also not a demand that you master pronoun grammar overnight — singular "they" has been in English for centuries, and if someone hands you "they", "he", "she", or a mix, using it is the whole ask. Get it wrong, correct yourself, move on. Nobody's grading you; they just want to be called the right thing.
On a dancefloor this stops being theory fast. Gender isn't the cover charge here — nobody clears the door by ticking a box. What matters is the same thing that always matters in this scene: you ask, you listen, you use the name and pronouns someone gives you, and you don't make their body your business unless invited. Nonbinary people have been in these rooms the whole time. The only new part is that more of us now have the word for it out loud.