tell (someone) what's what
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 naïve about the way you think this business operates, so allow me to finally tell you what's what.
See also: tell, what
Farlex Dictionary of Idioms.
- could tell (someone) a thing or two (about someone or something)
- could tell someone a thing or two
- can/could teach/tell somebody a thing or two
- could teach (someone) a thing or two (about someone or something)
- JFYI
- enlighten
- enlighten (someone) about (someone or something)
- Gen
- gen (someone) up on (something)
- keep somebody posted