Be in the know spoken language slang
To have lots of information about a topic that is usually not widely known.
He's a board member, so he's in the know about many things.
The killer tried to kill those who were in the know about his crime.
Susan is really in the know about the specialties in the town, so we can ask her to give us a food tour.
She asked everyone in the know to keep the secret about her pregnancy.
To tell someone the truth about something that they had not understood or received false information
Using someone else's personal information illegally without permission