This is one of the most misunderstood rules in all of prose fiction.
It’s important to understand that every single sentence you write is simultaneously telling one thing (the explicit/referential meaning of the sentence) and showing others (that which is implied or inferred by the sentence).
So, the famous example from Chekhov of “showing” by way of “light glinting in broken glass” is indeed “showing” the reader the light of the moon, because that is not made explicit but rather inferred by the reader. However, the sentence is “telling” us that there is broken glass and that light is glinting in it.
The general recipe for “show, don’t tell” is this: think about whatever it is you want the reader to feel or imagine or understand, and then don’t write that thing. Instead, write around it, so that the reader can feel what you are getting at by way of implication or inference.
Showing is always more evocative than telling, since the reader supplies the information from their own imagination, which is necessarily more vivid than reading it on the page. Showing uses more of the reader’s brain, and places the target image in their imagination, not just within their linguistic processing.
“Show, don’t tell” applies to all aspects of writing, including theme, tone, character, emotion, plot, setting, description, etc. You can show any of these things, or you can tell them.
For example, to “tell” emotion is to say, “John was angry”. To “show” the same emotion is to have John punch someone, or tell them to fuck off. Likewise we can identify “telling” for character, as in “John was the sort of guy to get angry easily”, for setting, as in “they were standing in a grocery store”, for description, as in “it was really dark”, and so on, all of which can be translated into “showing” statements by picking out the right sort of evocative details—details which imply or allow the reader to infer that which you intended to convey.
Many people wrongly equate “show, don’t tell” with a distinction between “scene” and “summary”. But this is only “show, don’t tell” as it concerns plot. It’s true, to “show” the plot is to write a scene, and to “tell” the plot is to write a summary. But this is only the the principle as it applies to the dimension of plot. “Show, don’t tell” is much broader than that. Similarly, many people wrongly interpret “show, don’t tell” as a caution against info-dumps or “expository lumps”. But exposition is only “show, don’t tell” as it applies to backstory, setting, or other information. Summary “tells” the plot, but it can simultaneously show other things; likewise, info-dumps or exposition, while it “tells” backstory or other information, can show other things. (For example, an info-dump about a historical artifact will “show” something about the narrator, or in the cases of dialogue, about the speaking character.) In both cases, an author might choose to use these techniques to “tell” something while effectively/artfully “showing” something else.
The question isn’t whether to show, it’s first what to show, and then how to show it. If you are writing fiction, there are many things you will want to show, including character, theme, emotion, plot progression, world-building (if you’re writing in the speculative mode), backstory, etc, etc. Ideally, you want to show multiple things with each sentence. A well-crafted story reveals multiple layers through the surface level of the text; a single line of description can simultaneously develop character, theme, and plot, without saying any of them directly. It shows multiple layers of meaning.
Many people wrongly believe that “showing” takes more words than “telling”. This is completely wrong. Effective showing is often shorter than telling. In fact, Hemingway (who along with Chekhov is one of the two most important authors for the “show, don’t tell” principle) talked about the “iceberg” theory of literature, where most of the story is hidden below the surface level of the words. Hemingway uses lots of simple sentences, but buries the emotion and character and theme below the surface, showing the story by hiding it “between the lines”, so to speak.
I think there are probably two reasons why people think “showing” is shorter than “telling”: the first, because they wrongly believe that “show, don’t tell” just means to use scene rather than summary, and of course scene is always longer than summary; the second, because the wealth of examples of “show, don’t tell” that you can find online are people taking simple descriptive statements, like “Sally was friendly”, and then replacing them with additional detail. These examples are indeed a form of “showing”, but it’s a limited aspect of showing that is probably better talked about in terms of “general/vague/abstract” language versus “specific” language, or more generally, the concept of the ladder of abstraction. Showing should in general be shorter than telling, because it is about cutting things out and letting the reader intuit or infer the meaning. Often, during editing, this can literally mean just deleting entire sentence rather than rewriting them. First drafts will often contain pairs of sentences, where the first tells and the second shows, something like: “Frank was distracted and he burnt the toast. He smelled burning toast and rushed to hit the button.” In this example, the first sentence can be deleted entirely, because it is shown by the second. If you go through and delete the first of these kind of paired sentences, your manuscript will be made shorter by following the principle of “show, don’t tell”. In other cases, showing is shorter because fewer words, rightly used, can convey multiple layers of meaning. This is probably easiest to see in the case of punchy dialogue, which can simultaneously convey characters, relationships, and plot.
There are many literary techniques for “showing”. For example, the techniques of metaphor, irony, understatement, ambiguity, and unreliable narration all depend essentially on what is not stated by the writer. Each of them, in their own way, refrains from telling directly, and instead shows just enough for the reader to comprehend the meaning on their own—these techniques all rely on the reader to do some work to find the underlying meaning, where it’s hidden between the lines. They are all examples of showing, rather than telling.
In literature, the written text includes narrative gaps that are filled in by the reader. According to some critics, in particular reader-response critic Stanley Fish, this is the distinctive feature of literature: plain-language is referential and expository, whereas literary language reveals additional meaning through intentional interpretive gaps. According to this view, “show, don’t tell” is not just advice on good writing—it is the essence of literature. Plain language puts the meaning in the surface level of the words (it “tells”) and literary language puts the meaning in interpretive gaps filled by the reader (it “shows”).
Before writing anything, you should figure out what it is you are hoping to express. You can think of what you want to express as the “target”—it could be a character trait, an emotion, a theme etc. The goal of “show, don’t tell” is to write in such a way that you express the “target” without saying it explicitly.