What do we mean by show? Think of this principle as presenting a picture—something readers can see if they close their eyes. Good showing also involves other senses, of course, but it’s easier to show this using the visual.
For example: I jogged through a San Francisco neighborhood. That sentence told you facts. If you can close your eyes and capture a scene, it’s because you have read something into the text that wasn’t there.
By contrast, here’s the way James Patterson wrote it: I jogged past yelping dogs running loose, lovers on a morning walk, gray-clad, bald-headed Chinese men bickering over mah-jongg. (First to Die: Little, Brown, 2001, p.104)
Patterson uses two senses and we see the dogs, the lovers, the Chinese, and we hear the dogs as well as the bickering. That is good writing, because he drew a picture for us and pulled us into the San Francisco scene. In one sentence, we jog alongside the protagonist and live vicariously.
Good writing is subtle. Sometimes one simple detail conveys more than a paragraph of descriptive words.