expression
what's what; heads or tails
Used in negative contexts, almost always as 何が何やらわからない or similar, to express complete confusion or inability to make sense of something.
See also: 何が何だか
説明が難しくて、何が何やらわからなかった。
The explanation was so difficult I couldn't make heads or tails of it.
初めての海外旅行で、空港に着いたときは何が何やらさっぱりだった。
On my first trip abroad, when I arrived at the airport I had no idea what was what.