Scenes
scene: in a drama, a subdivision of an act or of a play not divided into acts…."scene" is also the name given to a "dramatic" method of narration that presents events at roughly the same pace as that at which they are supposed to be occurring, i.e., usually in detail and with substantial use of dialogue. In this sense, the scenic narrative method is contrasted with "summary," in which the duration of the story's events is compressed into a brief account.
–The Concise Oxford Dictionary of Literary Terms
Scenes are one of the fundamental building blocks of narrative fiction - so fundamental, in fact, that almost all of the how-to-write books I looked at in the course of writing this post hardly talked about them at all, any more than they talk about spelling or grammar. The assumption seems to be that if you write at all, you already know what a scene is and how to write it.
The two key characteristics of a scene are place and time. The term originated in the theater, where the definition was basically "continuous action that happens in one place at one time, and when it's done we have to change the set or at least lower the curtain to let people know that we've just skipped a couple of hours." Characters can come and go during the course of a scene; the focus can change from one person to another; but the place where it happens generally stays the same and the scene itself runs continuously from start to finish.
Note that I didn't say anything about action. Stuff happens during a scene; people move, talk, punch someone else, whatever. But it's not the action that makes the scene; the scene is the container for the action. Place and time constrain what can happen. You're not going to see an army on horseback riding to battle if the scene takes place in Lady Grenville's drawing room; you're not going to write a half-hour argument if the scene takes place during a two-minute commercial break while the characters are watching TV.
Not that action is completely unimportant. A so-called scene that simply described several hours of an empty, unchanging drawing room doesn't make for much of a scene or story in most cases (though Ray Bradbury pulled it off in the magnificent tour de force "There Will Come Soft Rains.") In most cases, the point of choosing this place and that time interval to show as a scene is that one's characters are doing something interesting and story-relevant there and then.
Scenes are the "show" part of "show and tell." "They spent three hours in the library, hunting for the next clue" is a summary, not a scene. "They walked into the library. 'You take the shelves on the right,' Sandy told Bob. 'Dan, you do the ones on the left. I'm going up by the windows, and we'll meet in the middle.' Dan nodded. 'Yell if you find anything,' he said over his shoulder as he started toward the back corner. 'Anything at all.' The other two nodded soberly at his back and went off to begin the hunt." is a scene (an extremely short one, granted, but this is just a blog post, after all).
Scenes have a beginning, middle, and end, but except for the very last scene in a story or novel, the "end" of a scene is never a complete resolution; it leads onward. The action and events that take place here and now are over, but there's more going on elsewhere or later on that is or that will be important. That bit of openness at the end of every scene is usually some kind of unanswered question (Will the hero escape from the snake pit? What is Uncle Al doing while all this was going on? Who wrote that letter? Where did the cheese come from? Is she really in love with the lawyer? If the clue isn't in the library, where is it…or did someone else get to it first? What are the consequences of whatever just happened?), and it is a large part of what ties a novel together and keeps it moving forward.
What all this means is that scenes are where all the basic elements of writing - dialog, description, action, characters, setting, conflict, viewpoint, etc. - come together at once. Sometimes you can strip away some or most of these elements - there are scenes that are pure dialog, for instance - but that doesn't work as a regular thing. It's too abstract for most stories except as an occasional teaser (who are the characters behind these two voices, what is the mysterious stuff they're talking about, and why is it relevant to the rest of the story?).
Juggling all those other elements makes it easy for some writers to lose track of those key scene boundaries, place and time. A scene that was supposed to be a brief, tense dinner-table conversation drags on over dessert and coffee because the characters are still doing and saying things that follow one another and never seem to get to a good stopping spot, though they're long past the point of being story-relevant. Time - and the scene - just keeps rolling forward until all the characters finally go off to bed. This is why so many beginning writers seem unable to end scenes or chapters unless their viewpoint character falls asleep or is knocked unconscious; they're being true to life (in which we keep on doing stuff as long as we're awake) instead of being true to the story (in which most of the stuff the character does - dressing, eating, etc. - doesn't contribute anything to the story).
Asking "where does this scene start?" and "what is the end?" are important questions. Starting too early or too late, or stopping too early or too late, can throw the scene out of balance even if everything else is working just fine. If the scene is about the tense dinner conversation, it may be tempting to lead into it by starting with someone setting the table, but unless they're also poisoning the plates or rearranging the seating in a way that's going to cause trouble later, the table-setting is too early in most cases. The important/interesting action that's taking place here-and-now is the tense conversation; show that, with maybe a line or two of lead-in to keep things smooth, if you need it, and when the conversation is over, stop and move on to the next scene or transition.
If you're having trouble with this, try studying some plays. The scenes are all laid out right there in front of you, and since they're almost nothing but dialog, there isn't a lot going on to distract you from the structure of the scenes, especially their beginnings and endings.
