Non-binary
A gender that isn't exclusively man or woman.
Non-binary is an umbrella. It covers anyone whose gender sits outside the two categories most societies recognise — people who are both, neither, somewhere between, or something else entirely.
Under that umbrella sit many more specific words: agender, genderfluid, demigirl, demiboy, bigender, genderqueer. Someone might use one of those precisely, or simply say non-binary, or use both depending on who they're talking to.
Being non-binary says nothing about how a person looks, what pronouns they use, or whether they medically transition. Those are separate decisions, and non-binary people make all of them differently.