If you’re a fiction writer, you’ll be aware of the need to grab a reader’s attention as early as possible; to hook them, preferably, on your very first page. One key technique for doing this is to start your story in medias res.
The Latin expression in medias res means “into the midst of things”. Used as a literary term, it refers to starting a story by jumping straight into the middle of the conflict or action.
It’s often a temptation for writers to start by providing all the background information for their story, all the character and location detail they’ve laboriously worked out. But this exposition or “infodump” can be very boring.
A better approach is to skip the exposition, at least temporarily, and dramatize your work’s central conflict from the beginning. As well as immediately involving the reader, this helps set up narrative tension : the reader wants to know why the described conflict is happening. Explaining too much up front can deflate this intrigue. Over time you can slowly reveal the explanation in what will, hopefully, be a satisfying and engrossing process for the reader.
Filling in the back-story can be achieved in several ways : via flashback, for example, or by having your characters recall prior events. The skill is in providing the reader with just the information they need, without either overwhelming them or leaving them bemused. The best approach is to reveal your back-story in dribs and drabs so that a lot of the time, your readers aren’t even aware they are being informed.
Of course, there’s nothing wrong with writing long sections of factual information for your own use, as you work out the details of your setting. In many ways, this is a good thing. Just don’t expect your readers to wade through all that before they reach your actual story.