Argot vs Jargon

The confusion in the answers here arises that in different traditions (and different languages) jargon and argot are used to describe the opposite concepts. This is further complicated by the term slang which is gaining popularity and is more and more used to describe both.

But the problem is mostly with the labels, not the concepts. Essentially, there are three concepts that differentiate a particular sub-code of language based on the social context of its use.

1. Code used for professional and specialist communication. Commonly referred to as jargon but also occasionally argot or slang (some dictionaries of slang will include some examples of this code).

2. Code used for lower register (informal) communication by the wider community. This is the most common understanding of 'slang'. But under the French influence also referred to as 'argot' and also not uncommonly 'vernacular', 'demotic' or even 'dialect' with various nuances dropped or preserved depending on context.

3. Code used by outsider (often criminalised) communities often with the specific purpose of keeping communication secret. Most often termed 'argot' in specialist literature but commonly also described as 'slang' (e.g. Cockney rhyming slang).

So it is worth to always specify exactly what you mean by your terms if the distinction between these three is important. Otherwise, pretty much any of these three terms will get the general sense across.