As defined on Wikipedia, Augmented reality (AR) is a live, direct or indirect, view of a physical, real-world environment whose elements are augmented by computer-generated output such as sound or graphics. It can be considered an extension of Virtual Reality.
A video from Google..
Members of Project Glass Team at Google are testing augmented glasses.
The device features a band that stretches across the forehead and behind the ears, two nose pads, and a small rectangular screen that sits in front of the user's right eye. Required information will pop in real-time right in front of the user's eyes. The device presumably has built-in Wi-Fi and 3G/4G connectivity.
But every technology has disadvantages too..