Narrative voice can be loosely defined as the perspective the story is told from. There are many factors to be taken into account when choosing a narrative voice as the writer decides what response they want from the reader and what effect this will have on the story.
Choosing a type of narrative voice is important as there are many to choose from. For example, a first person narrator is a character within the story, telling the events from their perspective. These narrators are often unreliable to the reader as they lack omniscience (the full events are unknown to them, as they are recounting what they know and cannot see from another character's perspective) and their opinions can often cloud descriptions (a first person narrator can pick and choose what they describe about other characters, influencing their own opinions on the reader). First person narrators often use I, my, me, we pronouns.
Second person narrators are not commonly used by writers; adopting the personal pronouns you and your throughout the text.
Third person narrators tell the story as someone who is not a character, using she, he and they pronouns. These narrators can offer insight into the thoughts and feelings of characters but may not know the full story and often recount events as they are experienced by the characters.
With third person omniscient narrators, the story is told by someone who clearly knows more than the characters in the story. These narrators can recount events that happen simultaneously, for example, George sunk down in defeat, accepting the fact that he was lost in the thick woods. Little more than three miles away, a cloaked figure smiled.
When choosing a narrative voice, writers must think about how the reader will feel about the narrator and how reliable they are, as well as who the narrator is and what effect that will have on the story, how the narrator chooses to present the events.