Currently, I see ARGs (and games in generally) designed for three categories: education, marketing, and entertainment. Educational games tend to be relatively local and small, so they get less attention than the other types. Nevertheless, they're out there. When people talk about games, they sound as if they believe there's a vast gulf between these categories. I often hear comments like "I looked into GAME, but it's really just there to sell PRODUCT," "what's the point of GAME?" and "GAME sounds interesting, but it's educational." From a game designer's view, though, they're all much more alike than they are different.

At their core, games in all of these categories are trying to get some information across to the player. Educational games try to teach the player something of real-world importance. At their simplest, marketing games may merely be trying to tell people that a brand exists. More complicated marketing messages might involve getting across a specific emotion. Games designed entirely for entertainment often have the most to get across, since they have to teach you about the game world as well as how you can interact with it.

In the end, you can describe any game as education, marketing, and entertainment just by changing focus. For example, Super Mario Bros. teaches you about the biology of their world (mushrooms are soft, turtles are hard, and beetles are fire-proof). It also gets across some emotions (Bowser is a jerk) all while entertaining you.

All games have the same basic criteria. They have to be fun or nobody will play. They have to hit people's emotions, otherwise people won't care about the experience. And they have to help people learn or they'll be incomprehensible. Everything beyond that is just a matter of emphasis. In the end, all games are games.