"know what is what" in Chinese (Simplified)
分得清楚明白事理
Definition
能够分辨什么才是真正重要的，或者能够看清人或事物的本质，不容易被愚弄。
Usage Notes (Chinese (Simplified))
多为非正式语境，用来形容有经验、有判断力的人。常和'他很清楚分得清楚'等表达连用，强调实际经验和常识。
Examples
After years in business, she knows what is what.
做了多年生意，她已经**分得清楚**了。
You must know what is what before making a decision.
做决定前，你必须**明白事理**。
He doesn't know what is what yet—he's new here.
他还不**分得清楚**——他刚来这里。
Don't worry, I know what is what around here.
别担心，这里我**分得清楚**。
She pretends to be an expert, but she doesn't really know what is what.
她装作是专家，其实根本不**明白事理**。
After getting burned once, he learned to know what is what.
吃过一次亏后，他学会了**分得清楚**。