This document provides an overview of eye tracking technology. It discusses why eye tracking is used to understand human behavior and thinking. It also describes Tobii eye tracking technology, basic operating principles involving infrared light reflection, and applications in TV, web and street advertising. Eye tracking metrics like fixation time and gaze plots are explained. Advantages of eye tracking include obtaining insight into eye behavior without training, while disadvantages are expense and calibration time. The document concludes eye tracking can help develop video games and assist handicapped users.