First person point of view is a point of view in which an "I" or "we" serves as the narrator of a piece of fiction. The narrator may be a minor character, observing the action, as the character Nick does in The Great Gatsby, or the main protagonist of the story, such as Holden Caulfield in The Catcher in the Rye. In addition, a first-person narrator may be reliable or unreliable.
While first person point of view can allow a reader to feel very close to a specific character's point of view, it also limits the reader to that one perspective. The reader can only know what this character knows. Some writers, especially beginning writers, have a tendency to get stuck in first person point of view. It's helpful to at least try writing in third person from time to time.