Stories are organized around a sequence of events that contain plot drivers that influence what happens in that section. Throughout time, storytellers have drawn upon common story structures that have evolved within their culture.
In most stories, your protagonist wants something—to change a law or the government itself, to avenge a death, to hook up with the cutie, to dispel a curse—and your antagonist usually wants something that is in direct opposition of whatever the protagonist wants.
From those opposing wants come the narrative conflict and thus plot.
"Exposition" can be a scary word. In some writing circles, "experts" will warn you to exercise extreme caution when using it, or they'll make it out to be a difficult but necessary evil. But ultimately, exposition is just another writing tool, and it's used in all sorts of writing, even beyond fiction. Think of it this way: no matter what you're writing, you want your readers to understand and follow your train of thought.