expression
not knowing what's what; unable to make heads or tails of something
Expresses confusion when a situation is chaotic, unclear, or overwhelming, making it impossible to grasp what is happening.
説明が複雑すぎて、何が何だかわからない。
The explanation is too complicated; I can't make heads or tails of it.
突然の出来事で、何が何だかわからなかった。
Because of the sudden event, I didn't know what was going on.
Similar meaning of being unable to understand, but 何が何だかわからない emphasizes confusion about the overall situation, while 訳がわからない focuses on not understanding the reason or logic.
A fixed expression composed of 何 (what), が (subject marker), 何だか (what it is), and わからない (not understand). The repetition of 何 and the contrast between が and だか create a sense of total confusion.