When a narrator uses the pronoun "I" we know that the point of view is first person.
The point of view is the perspective from which a story is told. The point of view can be first person, second person and third person. While the first person point-of-view uses the pronouns "I" and "we", the second person point-of-view uses the pronoun "you". Moreover, the third person point-of-view makes use of different pronouns, such as "he", "she", "it" and "they".