Ah, the dreaded info dump! Exposition is a type of writing that is used to explain, describe, or inform the reader about something, but chunks of it dumped into one or more spots in your novel can really kill the reader's enjoyment.
If you're writing a nonfiction book, of course, exposition is an essential part of your writing, but in fiction it's more of a spice to be used sparingly. There are, however, a few ways to work exposition into your work without killing the flow of your story: hide it.
Dialogue
Your characters can say things that will explain what's going on to your reader. For example, if you're writing a story set in a foreign country, you can have a character say something like, "That's the traditional way of greeting someone here."
Internal thoughts
Your characters can think things that explain what's going on to your reader. For example, if you're writing a story set in a foreign country, you can have a character think something like, "That's the traditional way of greeting someone here."
Actions
Your characters can do things that explain what's going on to your reader. For example, if you're writing a story set in a foreign country, you can have a character do something like greet a person in the traditional way.
Show, Don't Tell
This is a writing advice cliche, but it's true. If you want to show your readers what your characters are feeling, describe their actions and thoughts in detail.
Give Your Readers Just Enough Information
Think about what information your readers need to know in order to understand your story. If you're introducing a new character, for example, you'll need to give your readers some information about that character. But you don't need to give them the character's entire life story. Just give them the information they need to know in order to understand the story.
Exposition can be a useful tool in your writing, but it should be used sparingly. If you find yourself dumping exposition into your story, take a step back and see if there's a way to work it in more subtly.
Pro Tip: Be especially vigilant about exposition at the beginning of chapters. Many writers start their chapters with a piece of exposition, but this can be a real turn-off for readers. If you find yourself starting your chapters with exposition, see if there's a way to start them in a more interesting way. Act first, explain later.