tell (someone) what's what

To inform someone of the true facts or most fundamental information (about someone or something). After putting it off for a week, Sarah finally told Jane what's what and ended their relationship. You're so na?ve about the way you think this business operates, so allow me to finally tell you what's what.

Common Names:

Name	Pronounced	Usage
Iosias	-	Biblical Latin, Biblical Greek
Ramona	[rə'məunə]
Noortje	NO:R-tyə (Dutch)	Dutch, Limburgish
Evgeniy	yev-GYE-nee, eev-GYE-nee	Russian
Halim	-	Arabic
Monique	mo-NEEK (French), mə-NEEK (English)	French, English, Dutch