Alternate Reality Game, in this case. It's a game that's meant to be played as though it were a real situation, typically involving the solution of some mystery through participation in arcane tasks that tend to be designed to feed into viral marketing efforts.
Maybe my brain is just being fuzzy, but I'm still a tad confused.
Is it 'played' in Realspace? Or is it an actual videogame which pretends to be realspace?
Or is it like Augmented Reality, where you have some sort of device which interacts with things/places in Realspace? Like, for example, a smartphone app I heard of which is a sort of team-based "king of the hill" game, where players use their phones to capture points around the world.
It's played in realspace, though it might be linked to a digital game or somesuch.
Here's an example that apparently ran for Bioshock 2, though the one I mentioned was less for marketing and more for fun from what I remember. Finding parcels and using the contents to figure out where the next one was I think was how it worked.
"February 2009 saw the launch of the ARG Something In The Sea, designed to promote the videogame Bioshock 2 by immersing players in character Mark Meltzer's quest to find his missing daughter. In addition to the messages, documents, photos and puzzles on the website, those following along on 8 August 2009, were given the coordinates of 10 beaches worldwide and told to go there at dawn. Those who did found objects planted by the game runners designed to look like they had washed ashore from Bioshock's fictional underwater city of Rapture. Players who wrote letters to Mark, whose address was advertised on the website, also sometimes received items such as wine bottles, records, or masks."