As the phrase suggests, an info-dump is when too much information about a character's background or the story's history is given at once. I've seen it disguised as conversations, class lectures, and prologues. It doesn't matter how it's presented, info-dumps tend to be boring.

This chapter is going to be very similar to the "Ease Up On Backstory" chapter because, in most cases, an info-dump is the result of excessive backstory. Some authors want the reader to know everything about the world they created, thinking it will enhance their enjoyment of the story. The truth is, it doesn't. It slows it down.

I've been a beta-reader to some early drafts, and one of these stories I read literally had the main character listening to a teacher give a full history lesson on the magical families. This history lesson spanned an entire page, and I found myself skimming past it because I thought, "Who cares about these families? None of them are hers! This is so boring."

About 3/4 of the way through the book, when a tiny portion of that history actually became relevant, some characters had a conversation to bring up the relevant point. That was the perfect way to bring up backstory. They gave me what I needed to know, when I needed to know it. Which made that entire page of history lessons completely unnecessary.

That's great, but the reader doesn't need to know all of it. Especially not all at once. It's like dating someone. You gradually get to know someone through conversations and observing their actions. It's not like a job interview where you hand the interviewer your resume in an attempt to sum up your entire working life. That's an info-dump, which is okay for employers, but not for story characters.

Give the reader tidbits. Whether it's the history of a race or a character's family background, let the reader gradually soak up an understanding of it. Let them "date" that backstory until, hopefully, they fall in love with it. :)