For those note familiar with Google Now it's a search assistant found within Jelly Bean. The service displays Cards or Snapshots of information that Google thinks you might need to know about. This could be as basic as offering directions to the restaurant you just looked up, or as sophisticated as poping up a reminder for an upcoming flight it found within an email on Gmail.
At present nothing official has been released on the possible implementation and nothing has been activated. But clearly the company has been working on porting its predictive search features over to the desktop for future possibilities.