Sorry for being stupid but...
What is an ARG?
Alternate Reality Game.
Its pretty much a massive puzzle using actual media as the hints. Generally a good arg takes a bit to "beat" because of all sorts of codes used, like Morse codes, binary text, hex code, etc. Sometimes its just hints inside of videos. Gotta look for extra meanings, since arg videos have no meaning at face value.
Valve is an example of a company that has made an arg before, leading up to an update.
It can be quite challenging and fun, but there are a lot of stuffty args.
Hope I explained that correctly.