According to reports from 9to5Mac, from now on you can use the camera of your PC / Mac to redeem iTunes gift card. Thus, the redemption process is faster and require less discomfort for the user. This is one of the new features of iTunes 11.
Process is same as Uber app, where app eliminates the annoying process to type in the number of our credit card, because the app identifies directly through the device camera.
Various reports over internet also suggest that this system is being implemented gradually, and that is only available in U.S. accounts at the moment.