何(なん)なのかwhat is it (that), the meaning of something, what something is about

彼(かれ)の発言(はつげん)の意味(いみ)が何(なん)なのかを考(かんが)える。

To think about what the meaning of his remarks is.

少女(しょうじょ)：「あの飛行(ひこう)物体(ぶったい)は何(なん)なのか…UFOなのか？」

Girl: 'What is that flying object... Is it a UFO?'

僕(ぼく)はこの訓練(くんれん)の意味(いみ)が何(なん)なのかを理解(りかい)出来(でき)ていません。

I do not understand what the meaning of this training is about.

壁(かべ)という壁(かべ)に黒(くろ)い点々(てんてん)がついているが…一体(いったい)あれは何(なん)なのか…。

Black dots are attached to every wall... what on earth are they...

境遇(きょうぐう)も価値(かち)観(かん)もまるで異(こと)なる彼(かれ)らが家族(かぞく)ぐるみで仲良(なかよ)くできる秘訣(ひけつ)は何(なん)なのか…？

What is the secret that allows them, with completely different circumstances and values, to get along as a family...?