Any length of text from a literary work can be identified as a passage. In most cases, a passage is referred to because the excerpt can be perceived as containing some sort of greater meaning.
In schools and churches, a passage is often examined from many different points of view. This shifting of perspective lends to a better understanding of either the story itself or the allusion that is being made by the story. When a passage is referenced by another literary work, it is cited, or validated with a source and used as a tool to further conceive other ideas that allude to similar schools of thought.