Narrative perspective refers to the set of characteristics that determines the method an author of a story uses to relay the plot to his audience. It encompasses both the narrator or storyteller, and the persona from whose point of view the story is told.
The most commonly used narrative perspectives used in fiction writing include third person limited, third person omniscient, second person and first person. Each narrative perspective differently affects the story and has its advantages and disadvantages.
The writer must consistently use whichever narrative perspective they decided to use at the start of the story. The only time this is not in effect is when there is a change that suggests the change was intentionally done for effect.