Literature bears a special relation to reality. Literature is an invention; it is a product of the imagination of the author, a fiction. The writer does not literally copy reality. One cannot say that the world represented in the work or the characters are true or false. Literature speaks of entities that do not require verification outside of the limits of the work itself. Although in a certain sense it can be a copy of reality, before anything else a re-elaboration should not be confused with reality itself.
Some literary texts distance themselves from reality more clearly than others, like fantasy literature; others are closer to reality, like literary realism. Even in these cases, there is always a manipulation of real information that sets the work apart from historical truth. While this attitude is inadmissible for a historian, it’s more than acceptable for a literary author.
Truth is not the criteria guiding literary creation, credibility is. Every story has to tell things in a coherent and credible way for the world it creates. It’s ruled by its own norms, which is known as internal logic.
All this is transmitted through literary language, which is a standard language used to introduce words that aren’t so common (uncommon voices, learned expressions, foreign words, archaisms, etc.), and that is typically subject to a form. On one side, it has many things in common with educated writing; on the other hand, it usually features some colloquial and even vulgar expressions, intended to cause certain expressive effects.