On jargon: when should you avoid it, and how to use it properly
Jargon is words that name concepts that are in wide use in a given field of scholarly or professional discourse. Their value is that they name a kind of thing precisely and as such can serve as a reliable currency in discussions in the field. Often, a jargon term is specific to a theory that has uses or followers within a field and is defined in that theory.
Sometimes scholarly thinkers and writers coin their own terms, and these then become jargon. For instance, in philosophy Heidegger's expression "Dasein," which in German means "being-there" and is usually left untranslated, is defined by him in a particular way; the same is true of Kant's uses of "phenomena," "thing-in-itself," and "a priori." Indeed, the French philosophers Gilles Deleuze and Felix Guattari argue in "What is Philosophy?" that every major philosopher not only invents new concepts, but that is philosophy's essential purpose. This is an uncommon view.
Jargon terms can be more or less precisely defined, or can have varying uses within a roughly delimited field of possible meanings. For instance, again in philosophy and "theory," the concept of "the subject" has several related possible meanings, depending on who is writing, and is, like Heidegger's Dasein, something like a certain way or aspect of being a person that is more or less universal. There are jargon terms in popular political discourse, such as "micro-agression" and "politically correct."
Jargon has the advantage that when used properly, readers will know exactly what you mean. Because either the meaning of the term is established in the field, or you establish your usage of it in your paper or book by stating precisely what you mean. This then saves you having to repeat a phrase of several or more words each time, and it also enables you to be more precise than might be the case if you used not the single term but a descriptive expression.
Jargon is misused when it is imprecise or obfuscatory because it appears to name something specific and yet fails to do so. This can happen when writers get carried away by the appeal of certain terms and feel somehow potentiated or ennobled by this. In philosophy and humanities "theory" this often happens when inexperienced writers are too absorbed in trying to think about a certain writer who uses much jargon, and failing to distance themselves from it, seem to want instead to further explicate the author's ideas by using the same concepts he does, and using concepts introduced and used in his works to elucidate or explain others. This usually fails. That is why commentators on philosophers and theorists, and this is especially true when the commentator is writing in English about theorists writing in German or French or in traditions first developed in those languages. The best writing of that kind performs a work of translation and deliberately aims to use an "ordinary" English prose style and terminology to clarify the meaning of the primary text's particular uses of terms, expressions, and manner of thinking.
When using special vocabulary, always ask yourself: What does this term mean exactly to me? And will it be clear to my writer with the same precision?