As I’ve talked about several times on here, most stories are made up of three different dominating plotlines, and most commonly, they are these:

External–this is the character’s outer journey. The character has a concrete goal, encounters an external antagonist, and struggles with the conflict to get the goal.

Internal–this is the character’s inner journey. The character has an abstract want, and in pursuing that, completes a character arc. The antagonist is the self.

Relationship–this is a relationship journey. The character either aims to draw close to or increase distance from another person (or maintain the relationship as is). The antagonistic force is what is upsetting that. How it is resolved completes a relationship arc.

In the writing community (specifically in screenwriting), typically the external and internal weave together to make up what people call the “A Story.” The A Story is seen as the primary plot.

The B Story is the secondary plot.