"Books in the Teen Paranormal Romance section should be arranged in alphabetical order by author's last name."There are at least two ways to understand this sentence. The speaker could be saying it's likely these books really are arranged in order. Or the speaker might be saying these books ought to be in order (whether or not they actually are). Without additional clues from tone and context, it's hard to say what the speaker intends to communicate.
We could characterize this ambiguity as descriptive vs. normative. A roughly similar set of terms philosophers use is mind-to-world vs. world-to-mind direction of fit. The question I use to keep these terms straight is:
Is the speaker trying to fit her mind to the world, or fit the world to her mind?Regular beliefs like "The books are in alphabetical order" or "It will probably rain here tomorrow" are attempts to align our minds with the way the world is; they feature mind-to-world direction of fit.
Meanwhile, attitudes like "These books should be in order, so put them in order if they're not!" are about shaping the world to our minds; they feature world-to-mind direction of fit.
This terminology comes up often in metaethics literature because one way to characterize moral realism is to emphasize mind-to-world direction of fit (we're just trying to hold true beliefs about the way the world is)...and one way to characterize expressivism is to emphasize world-to-mind direction of fit (morality originates in our attitudes).
Why bother with direction of fit lingo? Couldn't we just talk about beliefs and desires? For one thing, direction of fit is (possibly) a tidy way of explaining the difference between beliefs and desires. For another, there may be states of minds that don't reduce to beliefs or desires yet show direction of fit. Finally, philosophers sometimes wonder whether the story is so simple even for beliefs and desires, e.g. Terry Horgan and Mark Timmons question whether all beliefs have mind-to-world direction of fit.