Answer:
The answer is alternate reality game.
Explanation:
Also abbreviated as ARG, this is a type of game that uses reality as a platform. For example, the developers of a horror game might send you instant messages pretending to be a character of the game.
The ideas of alternate reality have been especially used for advertising campaigns. For example, an ARG called "I Love Bees" was made to promote the release of videogame Halo 2.
