فَيُطْلَبُ بِـ«مَا» شَرْحُ الِاسْمِ كَقَوْلِنَا: مَا الْعَنْقَاءُ؟
Mā can seek the explanation of a name, as in: What is the ʿanqāʾ?
Exposition of a name asks what an unfamiliar term signifies. The questioner has encountered a word but lacks a sufficiently clear idea of its referent. A suitable response explains the word's meaning or gives an intelligible description.
Such a question does not entail that the named object exists externally. Learning what a word means and asking whether anything corresponding to it exists are different stages of inquiry.