You can think of tone as the overall character or attitude of the story. For example, tone can be characterized as serious or informal. In To Kill a Mockingbird, Scout is the narrator, so her voice most affects the tone of the story. Since she is a young girl, her voice is innocent and simple. She doesn't understand things like the status quo because she's not yet an adult who has to comply with the rules of society. Due to this voice, the tone of the story is also more innocent and childlike.
