Jargon usually means the specialized language used by people in the same work or profession. Internet advertising jargon includes the terms "click throughs" and "page views."
This noun can also refer to language that uses long sentences and hard words. If you say that someone's speech or writing is full of jargon, this means you don't approve of it and think it should be simplified. In Middle English, this word referred to chattering, so its origin is probably imitative: it echoes the sound of chatter or meaningless words.