what does this quote from to kill a mockingbird mean "the things that happen to people we never really know . what happen in the house behind closed doors,what secrets"

This is one of Miss Maudie's quotes. It's a piece of advice that she gave to Scout in an attempt to explain Boo Radley. She wants Scout to understand that no matter what people believe they know, they don't know everything. That none of us really knows what goes on behind the closed doors of another's home. People have secrets, and every home houses some of the secrets of the people who've lived there.