You will notice there are two ways of saying "what" in Breton; pe and petra. Pe only goes with a noun. And petra only goes with verbs. Petra is really a construction from "pe + tra".
Petra eo hemañ? What is this? (Note: "Is" is a part of the verb "to be") Petra eo hennezh? What is that? Pe anv ho peus? What is your name? (lit. What name have you?) Pe hini? Which one?