It's not a dumb question. The entire interface that you use to play the game is referred to as "darkness", so if somebody asks you to for example submit a join request through darkness, they mean submit it using this website.
I got confused with this as well... On my Factions Web Page and filling out one of the many "Exams" they set... I was required to send a DM to two others... Obviously having used Forums so often, I mistook that for meaning a Direct Message or PM.
I gusess its one thing that you should always be aware of, SWC is a whole new breed if you will excuse my saying. So there are many new Acronyms to learn.
Just take a little time to make yourself familier with them and you will be fine. I am getting there and I only recently joined.