Most stories need at least three different types of plotlines to be successful. This gives the story more dimension and depth. While there are other combinations to choose from, by far the three most popular ones to interweave are the external, internal, and relationship journeys.
The external plotline is the character's outer journey; the objective is to get a concrete goal. He encounters antagonism and struggles with conflict. This leads to significant consequences that can alter his life. This is referred to as the plot arc.
The internal plotline is the character's inner journey; the objective is to fulfill the abstract want. The antagonist is the self, which causes internal conflict, and the consequences are related to identity, which creates the character arc.
The relationship plotline is the character's relationship journey; the objective is to increase or decrease distance with another person (or, in some cases, maintain the relationship as is). The antagonist is what endangers that, which leads to conflict. The consequences are the relationship arc.
While I have written about each of these plotlines on my blog, I haven't really covered the fourth most popular plotline. This is what I call the "societal plotline" (or in some cases the "world plotline").
What is the Societal Plotline?
The societal plotline is the journey of a society. The objective is a collective's concrete goal (which could have an abstract want behind it). The antagonist may be another collective, or an entity within or outside the group. The consequences are the way the collective arcs. We may call this a societal arc.
The societal plotline is arguably "bigger" in scope than the external plotline, because it involves groups of people (or entities at least). However, this doesn't necessarily make it the most important in the book or film. In fact, the societal plotline is rarely the primary plotline (the A Story). Most commonly, it is the quaternary plotline. It's nonetheless still very effective, and significant. And sometimes it is pulled up into a more dominating position, like when there is no internal plotline.
This is what happens in Indiana Jones. Indy doesn't really have an internal plotline, so it's the external, relationship, and societal plotlines that dominate his stories instead. Those are the three dominating plotlines.
In any case, I like to envision the societal plotline as fitting "above" the external plotline (since it is bigger in scope), and in a sense, adding dimension that way.
So, let's cover more of what this plotline is, and how to work with it, so you can write one that resonates throughout--and adds dimension to--your story.