One thing you don't want to do as an author is dump information into your story that has no bearing on the current problem. We are all encouraged to provide information about our characters and settings, but a birth to that moment description of the character is unnecessary. How your main character got into trouble as a child for silly incidents isn’t relevant, unless it relates to his or her situation now.
In fact, as with short stories, the information not related to the overall plot should be eliminated completely from the narrative. A brief description of a house should be relative to its importance to the story. We don’t need to know the size of each room, the location of all the furniture—or even if there are any furnishings if we never go into the house. What we do need to know is the house’s relevance to the story.
The same goes for dialogue, actually it goes more for dialogue. Don’t put in information not relevant to the moment in your dialogue. It’s stiff and unnatural. The reader will wonder exactly why the person is saying what they just did.
For example, two people at a sports event talking about great a player and what an awesome move that person just made. Then in the middle of their discussion, one of the speakers says “he’s great as the head of the chess club.” No inclusive “too” to make it sound like the guy isn’t just a jock but also thinks logically. No previous introduction about this amazing combination of agility and brains, just an insertion that the person is in the chess club. Completely out of place and unnecessary to the current situation.
Your reader is now thrown off track. They’re confused about why you thought it necessary to bring in this information at this point. And they should be.
One of the worst mistakes you can make is to deviate from the main plot and have the reader wondering about a situation that won’t arise until later in the book. You will lose a reader, possibly earn a poor review, and in all likelihood have the word go out that your books don’t stay on track.
Authors owe our readers a pleasant reading experience. That doesn’t mean the storyline doesn’t have to get intense, or that the story should be an easy read, but we cannot throw them off the track of what they’re reading.
Remember: information dumps do nothing for your story. Save them for the background file, to be used when necessary, and sparingly.