"Ki ön?"

Translation: Who are you?

[jlsr2]

Why not "Ki vagy"?

[Floriaanva]

You here is meaning (you, plural) right ?

[vvsey]

No, actually, this is a singular, but formal, you. "Ön".
The plural version is "Kik önök?"

Both translate to "Who are you?"

[wyqtor]

So there is no form of to be here because ön requires the 3rd person verb forms, and those are left out when describing something?

[vvsey]

Exactly! :)

[MartinYoun8]

That could be a bit disrespectful in English. Not in Hungarian?

[vvsey]

Well, "ön" is a respectful form already but, sure, it could be said in a disrespectful way. It depends on the situation. There are definitely more polite ways.