In most books, there’s a character (or characters) who I like to call the Outsider. An Outsider is a character who doesn’t belong in a book’s world, whether it’s fantasy or sci-fi, or even a police procedural or medical drama. Because they don’t belong in the world, they ask lots of questions, and give the author the chance to explain things.
For example, Harry Potter in an Outsider in JK Rowling’s wizarding world because he doesn’t know what all the magical terms and items are. In Pirate of the Caribbean, Elizabeth Swan serves as an Outsider, because she’s clueless about all the pirate-y stuff.
Outsiders are important, because they act as an extension of the reader inside the book. Readers are effectively Outsiders too, but they can’t ask questions. If you’re writing a fantasy, your readers don’t know why the Kingdom of Somefarawayland has the best stronghold in the land, but they can’t exactly ask the writer, can they? This is where the Outsider is important. They can ask why the Kingdom of Somefarawayland has the best stronghold, and then the All Powerful Wizard can explain why.
Outsiders can also occur in earth-settings, such as in police stations and hospitals. An Outsider to a hospital might be the mother of a sick child who needs a doctor to explain to her (and the readers) why the child needs to be given a certain drug.
There can be several different Outsiders in each story, and they can all be different Outsiders for different settings. In my WIP, the protagonist is an Outsider in the mercenary world, while the sidekick is an Outsider to the world of archaeology.
Without an Outsider, writers have to insert (sometimes lengthy) descriptions to things, without being able to break it up into dialogue. I once read a book without an Outsider, and the author always had to break up the action to include a description of legal procedures and law terminology.
For the comments, who are your Outsiders, and what worlds do they help readers to understand? Let me know!