What's the difference?

Hello all,

I am new to the group and wish to ask what may seem a simple or 'dumb'
question:

What are the differences between the following?
alt-langs
art-langs
aux-langs
con-langs
(are there others?)

>From what I've gleaned so far, it seems many people use these terms
interchangeably, but that there are a few who feel strongly about the
differences between each, and are meticulous in their differentiation.
However, I have been unable to find any 'official' stance, and am
asking the question here, because I have a hunch that it may be more a
matter of opinion (and a decision made by collective opinion) than
anything formally defined.

Please bear in mind that it is _not_ my intention to stir the cauldron
or bring out any form of 'mine's better than yours' or 'aux-langs are
a more noble endeavour than con-langs' competition - just an
explanation/definition.

Many thanks and kindest regards,

Tom W.