Point of view refers to the perspective through which we view a story. There are three main points of view: first person, second person, and third person. There are, however, divisions within these broad categories of points of view. In a first-person point of view, a story is told from the perspective of the narrator using the pronoun "I," which allows readers to get inside the narrator's head and see things through his/her own eyes. The narrator is also an active character in the story. In second-person point of view, the story is told using the "you" pronoun, and only the "you" is the active character. In third-person point of view, a story is told using pronouns like "he" and "she." In third-person point of view, the narrator is not a character in the story, is removed from the action of the story, and relays the story from an outside perspective.
We can tell from the very first sentence of David Leavitt's short story "Gravity," which uses the pronouns "his" and "him" that the story is told from the third-person point of view:
Theo had a choice between a drug that would save his sight and a drug that would keep him alive, so he chose not to go blind.
Since Theo is being talked about as if an outside observer is watching him, we know that Theo is not the narrator himself; therefore, the point of view can only be in third person.
Yet, there are also three different types of third-person narration: third-person omniscient, third-person objective, and third-person limited. The omniscient third-person narrator sees and knows all about the characters and can even get inside the characters' heads. The objective third-person narrator can only relay the action seen in the story and the words said aloud. When an author uses third-person-limited point of view, the author focuses on one character for the story. The narrator can only get inside the head of that one character, so the story, though relayed in third person, is told through the eyes of the one character as she/he sees and understands events.
As we continue to read, we see that the narrator relays events of the past, such as Theo observing the world through glasses for the first time. We also see the narrator relay the thoughts of both characters; for example, we see that Sylvia doesn't care if people stare at her son while he wears her gigantic glasses, and Theo compares the visions he is seeing to the crystal clear images in a comic book. Since the narrator is able to relay both past and present and both characters' thoughts, we know the third-person narrator can only be an omniscient narrator.