Subplot • [Storytelling] • a less developed story hinged to the main story • Subplots are often misunderstood to be secondary subordinate stories running in parallel to the main story. Such secondary stories are a valid storytelling technique but they are not Subplots. A Subplot in not a separate independent story but an amplification of a branch or aspect of the main story. Each Subplot is, indeed, a story in its own right but it is connected to the main story through one of the objective characters. This objective character does double duty as the Main Character (a subjective character) in the subplot. As a result, it is inappropriate to hinge a subplot around either the Main or Obstacle Characters of the main story as the two story lines would become blurred and create confusion as to the message intended. In order to keep Subplots from appearing to be the main story, it is important to draw them with less detail. This does not mean they should be incomplete or sketchy, rather that the Subplot should be explored in less depth. There can be as many Subplots as there are objective characters. A large number of subplots will become unwieldy, however, and can needlessly complicate the telling of a story, blurring or diverting the audience’s understanding of the main story. Similar to the Main Character of the main story, the Main Characters of the subplots should be limited to one story each. Not all “multiple plot” stories consist of subplots attached to a main plot. Frequently in serial programs such as soap operas, certain forms of episodic television, and some written serials such as comic strips, several complete stories run in parallel, connected only by their common setting or by using the same ensemble of characters. In this form of storytelling, characters do double duty, playing multiple roles in a number of separate plots which really do not directly affect each other. The point of note is that an author should be aware of the difference between subplot and multiple plot constructions so that the proper dramatic connections can be made to create the greatest impact.
From the Dramatica Dictionary