An Alternate Reality Game (ARG for short) is an emerging form of entertainment with the internet at its heart. Combining elements of online community, puzzle-solving, treasure hunts, and cocktail parties, an alternate reality game gives players the thrill of living dangerously and being in on something edgy and clandestine without the expense of special gaming consoles or equipment.
Instead, an ARG tweaks elements of real life to lead players down a path that tells a story - and lets them help shape that story.
Websites are usually used to coordinate the game, taking advantage of the internet's inherent "is this really true?" factor. Usually, a website sets up a mystery and provides clues for players to track down a solution - one leads to the next, and branches out from the internet with phone calls from fictional characters, real newspaper ads with hidden messages, and players gathering in real venues to experience staged events.
Some examples of high-profile Alternate Reality Games include:
Year Zero - Trent Reznor's solution to doing a concept album in an age where MP3s don't come with liner notes and cover art. He pulled fans into an alternate world described in his dark, apocalyptic music. It ended with a private concert for those players who could follow the clues to the final venue which was interrupted by a staged police raid.
-- Wired Article
-- Nine Inch Nails Album Site
-- Wikipedia Entry
Art of the Heist - Audi introduced a new car model by setting up a theft at a car show and letting players track down the culprits.
-- Business Week Article
Audi Press Release
-- Wikipedia Entry
Last Call Poker - The story behind a console video game called Gun, set in the old west, was introduced through an online poker site where players discovered some of their opponents were ghosts and tracked down their tragic history. Groups gathered in graveyards to solve puzzles.
-- CNET Article
Marketing Company Brief
The Lost Experience - A website for the fictional airline featured in the show talks about the loss of the airplane and explains why no one is searching for the survivors on the island. They even got an executive from this non-existent company onto a late-night talk show to give a straight interview about the families of the characters on the show petitioning the company to go look for them.
-- ABC News Article
-- ABC's Lost Experience Site
-- Wikipedia Article