I recently gave up on an historical mystery I was sent as a reviewer that had this piece of dialog between two people employed by the queen: “Our lady queen’s past fifty. An heir’s out of the question, so the marriage game won't keep France and Spain at bay any longer. They want Mary of Scots on the throne and England back in their Catholic pockets.”
Don’t you think they both already knew that? The only reason one character said it to the other was to let the reader know what was going on.
Stories set in a world unfamiliar to the reader often face this problem, as author Jed Hartman explains:
"And now," Dr. Zurückgeschichte said, "please explain to me how an infodump works."
"But why would I have to explain infodumps to you, Doctor?" I asked. "You invented the infodump! And it has become one of the basic principles upon which our society is founded!"
To read more about “Faux Dialogue Naive (in which one character explains something to another character designed to be the reader-identification character, a character who doesn't have the necessary background and thus must have it explained to them), Faux Dialogue Redundant (in which one character explains something to another character who knows it already, as I am doing now), Faux Thought Redundant (in which a character thinks something to themselves that they already know), and Narrative" click here.
Janet Burroway's Writing Fiction suggests this solution: Instead of having one character say: “My brother is due to arrive at midafternoon and is bringing his four children with him” try “That idiot brother of mine thinks he can wlak in the middle of the afternoon and plunk his four kids in my lap” or “I can’t wait until my brother gets here at three. You’ll see - those are the four sweetest kids this side of the planet."