We determine a story's point of view by the narrator's position through describing settings and events.
The first-person point of view is used when a character tells the story. They use the word "I" to describe what is happening. They can write about the feelings and reactions to events that unfold from their point of view.
Example: I woke up late and missed the bus to school.
Stories written from the second-person point of view is when a story is told to you. This one is common in nonfiction writing.
Example: You are reading the descriptions of different points of view found in writing.
Third-person stories are written by a narrator who is not part of the story. "He", "she", and/or "it" are used to describe characters in the story. The narrator may only know what one character knows (limited), what a few characters know (multiple) or what all characters know (omniscient).
A narrator who is also in the story is telling the story from the first-person point of view. They're putting themselves in the story.