To know what is what is to understand how things really work. She knows what is what.
To know what is what praises practical knowledge rather than book learning. The people who know what is what in an organisation have usually been there longest.
1phraseknow what is whatTo understand how things really work.
“Ask the caretaker, since he does know what is what around here.”
know what is what is a phrase.
Practised in Idioms