External refers to what’s happening outside of characters’ minds. It’s the stuff that an observer could see. You could film it pretty easily. Internal refers to what’s going on inside a character’s head: feelings and thoughts. Prose storytelling regularly informs us of characters’ interiority in ways that, say, a screenplay cannot.
Robert Olen Butler describes 5 ways the people express emotions. Writers can use these expressions to help build better character interiority. Here, his 5 expressions and an accompanying journal exercise.
So, first of all, it’s worth noting that most of the story’s momentum comes from the “What’s going to happen next?” question, and that’s a question that arises from present-time story. Most of the story’s meaning, however, arises from the time digressions.
I introduced this concept of scenes vs. summary in my post on the four ways to break down page-level craft. Here, in more detail, is what scene vs. summary is all about. And I’ve included some explanation on how the story writer can benefit from knowing this aspect of craft.
Here are four ways to break down what can be included on a page. There’s some overlap between these, but it’s helpful to consider these four breakdowns when you’re crafting your scenes.