1. the "feeling" or emotional aura that pervades a story or a poem - atmosphere
The atmosphere is the air you breathe, the invisible stuff that surrounds. An atmosphere of a story or poem helps to communicate the theme or author's attitude towards the subject.
2. a critical moment in a story at which the protagonist is forced to take decisive action - Crisis
Critical = crisis. They are from the root word crit which means to separate or choose. During a crisis, the protagonist is forced to make a difficult choice. This usually results in some type of internal conflict for the protagonist, creates a learning experience which makes the character dynamic, and often is the climax of the story.
3. the time and place in which the story occurs - setting
The setting is where the story is set. Time and place. Sometimes it helps to think of a movie set. On a movie set, the director is creating the specific place and time in which the story takes place.