What it is
The info dump is when you take all that fascinating world-building, all that back story for your character, all the rules of your world... and you just drop it into the reader's lap in a big sloppy mess.
For instance
Let's say this is the start of your book. This is a hypothetical example, but I have encountered several stories lately that featured a first page/chapter very similar to this:
(note--the weird subject matter is just the first thing I thought of, sorry for the randomness)
Margie stood on the pier, watching the children splash and play in the water before her. When one of the children got too close to the edge, she hurried to catch him. Her shoulders itched with the desire to grow wings, because Margie was a Lylis, a magical creature that looked human but was actually a type of fairy, but she forced herself to jog instead.
There were actually four subspecies of Lylis--lotus, rose, lily, and amaryllis. Each species had a specific color of wing and a specific duty to fulfill in the world. Margie was a Rose Lylis, which meant she had pink wings and a duty to protect all children. But right now she didn't feel like protecting children. She wanted to get married and have children, but all Lylis were barren, unable to have children of their own...
Okay, that's enough of that. Do you see what was wrong there?
Well, there were a lot of things wrong with it...
But let's talk about that info dump.
If I was reading a book where this was the first page, I would put it right back down and not pick it up again. I want to read a
story, not a textbook. Not a history lesson. Not a lecture on the various types of "Lylis fairies." This is boring. I'm not attached to the character yet. I will not slog through all this exposition if I have nothing enticing me forward.
A better way to convey the same information
Margie stood on the pier, her eyes tracking the movement of each child's flailing arms and legs as they splashed in the waves and scattered droplets through the air like diamonds. At the moment, she wanted to be anywhere else. But as a Lylis, a fairy protector of children, it was her duty to stay and watch no matter how much it pained her.
She spotted one of the children on the end of the pier, tottering towards the edge. A baby. His mother sat on the beach, her nose in a book, and Margie didn't waste time trying to get the woman's attention with a strong gust of wind. She moved swift and silent as a shadow. Her shoulders itched to grow wings, but she forced herself to jog instead. People might be watching, and not everybody was susceptible to the blinding spells that kept her veiled from human eyes.
She reached the end of the pier. The child gazed up at her with eyes as blue as the water below. Young children could always see the Lylis. "Dahh," he gurgled, stretching out one sticky hand.
Margie scooped him up, ignoring the twinge in her chest at the way the baby fit perfectly into her arms. She wanted to have children, not just watch them. But unfortunately, it didn't work that way for fairies.
At least not the Lylis kind.
She set the child down by the water and watched him toddle off to his mother. Her arms were suddenly too big, too empty without him. Eternal barrenness--and the ache that accompanied it--made Margie's job a unique kind of torture.
The second example certainly isn't perfect either, mind you. I just dashed it off, so it's just a rough draft and could probably benefit from some reworking. And it's still a bit too "to the point" for me, at least for a novel. (It might be just right for a short story, though, where space is limited and details do have to be tossed in quickly.)
But see how I wove some of that information in with actions and thoughts? And notice I didn't even include all of it, like the Rose and Lily category stuff. It's totally unnecessary for the reader to know every type, color, and job description of a Lylis fairy at this point. That can all be explained later, when the reader is already interested in the characters and ready to know more about the nuances of the world.
So...
In short, don't waste valuable time at the beginning of the book pontificating about the rules and details of your world and the creatures in it. And when you DO include information, blend it in gradually like you're stirring sugar into cake batter. Don't just lump it all at the front and call it a day.
