Exposition occurs when writers 'tell' rather than 'show'. If you've ever wondered what an editor means when they talk about telling vs. showing, the three below are bad examples. I've copied them for convenience's sake, followed by a critique in red:
Example One – half way through this story, a secondary character, Mike, is talking to Zack, the protagonist and newcomer to their Bio-Dome: “The Outlands get so romanticized here. I mean the Bio-Domes have their own sustainable food sources that produce real vegetables and alternative protein sources such as soy, along with energy reserves from capped gas wells, orbiting solar satellites, and nuclear plants. The prices are exorbitant and we still have to supplement our dietary and energy needs with recycled waste. We don’t like to dwell on that much, but if you’re looking for employment, food reconstitution is a growing industry, and the perks make the downside worthwhile – medical is free, for example.” The writer is taking a short-cut. Instead of Mike and Zack walking through any of the described settings, or Zack discovering these things on his own, Mike fills him in. Further, the dialogue is a mouthful. Who talks like this? This particular kind of exposition is also known as an 'info dump'.
Example Two – the narrator opens the story with an opinion about alien sightings, and then introduces Mitchell, his main character: “Alien sightings have been, as we all know, hoaxes, the products of mischievous jokesters or greedy opportunists designed to attract attention or money from whomever they can con or milk for cash. Others who say they have seen aliens are usually victims of their own hyperactive imaginations. Despite knowing all of this, Mitchell could not rid himself of visions of grey-skinned aliens coming towards him with probes, while saucer-like ships hovered above his house, waiting for him to emerge, all of which on the surface seemed so dream-like, but which, he also knew, were horribly, horribly real.” The writer opens with the narrator sharing an opinion with the reader, which can be a form of telling. 'As you know', or in this case 'as we all know', is a big flag that exposition is sure to follow. There is also a shift in the narrative from the narrator speaking directly to the reader, to the narration becoming third person limited (beginning with, 'Despite knowing all of this, Mitchell could not rid himself....'). This shift in Point of View (POV) jars. I'll talk more about POV in an upcoming post, but generally, writers should maintain a consistent point of view throughout a scene.
Example Three – the narrator, a secondary character, opens the story by introducing us to her protagonist, Candas Cornwall: “Had she lived longer, Candas Cornwall might have been known as Fireslyph, Queen of the Stars. In telling Candas’s sad story, I do not promise objectivity, for even though I only knew her for a short time, I treasure the lessons she taught me. Should I seem overly sentimental, it is only because of the wisdom she imparted, and secondarily her virtue, beauty, and youth, which is now lost to us and this remorseless world, forever.” Again, the narrative opens with the narrator telling us about Candas Cornwall, also illustrated by her saying, 'In telling Candas's sad story....' The opening is also a frame - it presents a story within a story. When frames are 'told' by a secondary character, reader interest drops (most of us would rather read about a protagonist directly). Predictability is also a problem. Because the writer tells us that Candas dies, we know the end, so any dramatic tension built is lost. Finally, in an attempt to be dramatic, the writer goes overboard, heading into purple prose territory with a trite cliché - 'this remorseless world, forever."