According to an article on Information Week, Google classifies mobile users into three behavior groups:
The “bored now” are users who have time on their hands. People on trains or waiting in airports or sitting in cafes. Mobile users in this behavior group look a lot more like casual Web surfers, but mobile phones don’t offer the robust user input of a desktop, so the applications have to be tailored.
The “urgent now” is a request to find something specific fast, like the location of a bakery or directions to the airport. Since a lot of these questions are location-aware, Google tries to build location into the mobile versions of these queries.
I think it’s a pretty accurate categorization, and a good thing to keep in mind when you’re building your mobile site or app. Each “type” of user is interacting with your content with a different goal in mind, and the experience should be tailored accordingly.