Have to wonder what they all do... (image from GoNintendo)

They don't particularly 'do' anything.  A piece of software would be programmed to do a certain thing when it sees a particular image.  ie they could make it do the same thing no matter which card it sees, or have the Zelda one do something different from the Pikmin one depending on the game.

Here's what they'll be used for: (credit GoNintendo again)

We now have an explanation for the multiple augmented reality cards, and it's not as exciting as many were hoping for.

- six options for six AR games
- one game puts Miis in the real world, and then allows you to move them around and change poses
- you can also move around in the real world to get a different look at the Miis
- these cards put Samus, Kirby, Mario etc in the real world
- take pictures of posed characters
- includes sound effects for each respective character
- get all characters on-screen at once
- another AR game is a Billiards style game
- this wraps around your 'terrain', puts obstacles in your way, and then leaves you positioned behind a ball
- move around the ball to aim, and hit A to hit the ball
- hit a target that is around/past the things in your way

So, if my math is correct, we know four of the six AR games. Mii viewer, Star viewer, Billiards and Shooting. I wonder what the other two are!

very nice

Absolutely nothing...