Jargon: Technical terms; terms of art; terms of trade - words that are widely known and used only in limited circles of people who specialize in a science, art or trade.
1. When one talks or writes of things that are not widely known and that may have all manner of uncommon or special features, it may help a lot to introduce new special terms (or use old terms with specially given new meanings).
However, jargon also is often used to given oneself airs, to obscure or obfuscate, or just carelessly, and anyway has the property that when it is not addressed to the specialists for whose ends it exists that it makes for unnecessarily difficult prose.
In short: Jargon should be avoided, except in circles where it really belongs to the terms of the trade. Speak plainly, or don't speak at all!
2. There is, alas, a rather large amount of philosophical jargon - for which reason one may fondly imagine that a few gifted persons may have some use for the Philosophical Dictionary that contains this lemma.