My view of Augmented Reality is that it is basically adding to the real world what you might find useful. I believe that the best way to describe it is to say this:
When using a mobile device or computer it has to have a video camera to display extra content on top of it, like layers in Photoshop.
The Nearest Tube App for the iPhone is an excellent example of what I think Augmented Reality is, this is also one of the things that got me interested into augmented reality in the first place.
http://www.acrossair.com/apps_nearesttube.htm
A Definition of Augmented Reality
❝ There are two commonly accepted definitions of Augmented Reality today. One was given by Ronald Azuma in 1997. Azuma’s definition says that Augmented Reality
- combines real and virtual
- is interactive in real time
- is registered in 3D ❞
Extract from Wiki: http://en.wikipedia.org/wiki/Augmented_reality