Though many computer applications and operating systems make use of real-world metaphors like the desktop, most software interface design has little to do with how we actually experience the real world. In lots of cases, there are great reasons not to directly mimic reality. Not doing so allows us to create interfaces that enable people to be more productive, communicate in new ways, or manage an increasing amount of information. In other words, to do things we can't otherwise do in real life.
But sometimes, it makes sense to think of the real world as an interface. To design user interactions that make use of how people actually see the world -to take advantage of first person user interfaces.
First person user interfaces can be a good fit for applications that allow people to navigate the real world, "augment" their immediate surroundings with relevant information, and interact with objects or people directly around them.