In Jamaica Kincaid's "Girl," narration is used to highlight the constant expectations placed on young girls during their childhood.
The story consists of an onslaught of instructions delivered, presumably, from a mother to a daughter. As the long list of instructions progresses, it becomes clear that many of these rules and expectations are heavily gendered and would not be placed on a young boy living in the same circumstances.
The girl is reminded how to be polite, how to appear chaste, how to avoid looking like a "slut," and how to take care of the men in her life. In the tone of the daughter's few interjections, her mounting frustration and exhaustion are evident—by the end, she feels so weighed down by the expectations placed upon her that she barely cares about her mother's intentions in placing them.
Narration and plot are similar, but they're not identical. A story's plot is what happens in the story, while narration is the way the reader is told what happens. In the case of this story, narration takes on multiple roles—because it constitutes the entirety of the text, it explains the plot, characterizes both of the characters by demonstrating how they interact, and creates context for the world in which the story takes place.