Let’s take The Scarlet Letter. Plot is “What happens to a town in the 1680’s when a woman becomes pregnant outside wedlock?” After that, I think of it as events that propel the plot forward. There may or may not be a resolution, much fiction is written to ask a question and let the audience think about it. One thing many writers and teachers have said is that “good writing advances the plot”. So, if we have some characters acting quite oddly and out of sorts, not able to say something straight out (or the damned phone rings, or someone interrupts, or the monster comes back) I tend to see that as bad writing.
(The phone thing really gets me. That or just letting the phone ring. It’s something that makes me walk out or change channels.)