kitchen talk

Other people's business talked about behind closed doors that can't be said in public, but can be expressed in one's home kitchen, far from the person(s) being talked about. Usually one's opinion is expressed.

Don't talk about Jerry's affair here at work! That's kitchen talk.

kitchen table talk

A discussion between family (e.g. cousins) or close friends at a table or other private setting, where the two (or more) of you can have completely open, often deep, conversation. The key to kitchen table talk is the ability to throw the dirtiest shade, talk shit, and spill piping hot tea, that would not be typically be acceptable in every day society.

What happens at the kitchen table, stays at the kitchen table.

Girl 1: This is going to sound really shady, but...
Girl 2: It's okay girl, this is kitchen table talk.