There are quite a few rules in writing that come up in any writer's group, class, or instructional book. Don't use so many adjectives. Show, don't tell. On and on it goes; each one meant to help writers avoid common mistakes and craft their work into the best possible product.
All of these rules are well-meaning tips, meant to assist and shape young writers into skilled experts. And one of the most commonly discussed is "no info dumps." An Information Dump is when a writer gives a large block of information or background in one section, often through dialog but sometimes narration, without interruption and description.
The rule says that you should spread out this information through a story, weaving it through the book naturally and "organically" so that it feels like part of the narrative rather than a lecture. This is almost always ideal because it leads the reader along without slowing the tale with a block of information. Take character descriptions as an example. You can either do it in one or two paragraphs (as they look in a mirror at themselves), or you can slip bits through the book in bites.
Bob brushed his long hair back out of his eyes.
Sarah's long legs curled under her as she sat.
Gorthax fingered one of his intricately carved tusks as he pondered my fate.
By doing this, you give the reader information about the character in bite sized bits which makes it easier to remember by each bit being dynamic and interesting. By the end of the book you have the full description. And this is effective - its my preferred way of doing descriptions.
However, this push to avoid the info dump at all costs is pretty new; older books do it all the time without the slightest shame. For example, nearly every Sherlock Holmes story starts with a big fat info dump by the client with few interruptions. Its gone out of style, but there's valid use for the device.
|Holmes prepares to explain it all again|
The purpose to these rules is to help new writers, not restrict capable ones. H.P Lovecraft used adjectives to the degree it would make a modern editor or creative writing prof rip out their hair in horror. J.K. Rowling ends every single one of her books with a massive info dump explaining what happened and all the background stuff her characters could not possibly understand or know, because they're children. As I wrote in my post on The Rules a while back,
And so on. As you become better at writing, then you can start to bend and even sometimes break the rules because you've become skilled at what you do to the point that you can carry it off. But until you get there, those rules help you learn and stay on target.
Because none of us start out great at anything except being selfish and loud as babies. You have to learn to bat and throw before you can make the baseball team, and even then you're a long ways off from starting on the Yankees. Writing is no different. Study, practice, work, learn, and write, and you get better and better. The rules are there to help you with that.
And there are some genres in which the info dump actually is preferable and useful. If you're writing a zombie/reality show urban fantasy mashup then a block of description doesn't make sense. But if you're writing a hard boiled detective novel, then its almost required. Mysteries and detective novels need information in dry, hard format to give clues without manipulating readers or tipping your hand.
Mentioning this character has a button missing on their sleeve might be the eventual clue that reveals the killer, but readers need to know that information in the name of fair play (giving the reader everything they need to know in order to solve the crime). But if you mention that in isolation, it grows in significance to where it is to easy to pick up. Plus, the genre is generally narrated by experts in the field or through their perspective, and the block of description like something jotted down on a notepad or police report is how they do things. It pulls the reader into the story and helps them feel like the detective.
Another genre where the info dump is typical and useful is the period romance. Some, especially Edwardian or Regency romances, revolve around clothing, appearances, balls, and parties. Characters are revealed as if they stepped through the door and posed dramatically on the balcony before descending the steps revealing daring glimpses of their ankles. That's a perfect place for the info dump.
So its a question of wisdom and talent, and delivering it well and judiciously rather than an absolute rule, I believe. Like all the rules, it depends. It depends on your skill, the genre, the setting, the pacing of the book, what you're trying to accomplish, and a lot of other things.
And learning those things is a matter of study, practice, and understanding, as well as raw talent. Which is why the rules exist: until you get there, follow these and they won't lead you wrong. Ignore them and you'll tend to go astray.