Both :-)

I use them quite a lot, but that's a function of what (some of) my social circle cares about. If by "generally", you are referring to the general public, no, probably not.

mostly exist to distinguish people-in-the-know from the unenlightened masses?

jducouer taught me a wonderful (yiddish?) word that means that entire phrase: "shibboleth". Now *that* is a word which is really useful!