This document discusses different eye tracking methods and techniques. It begins with an abstract that outlines the purpose of eye tracking for human-computer interaction applications and some key techniques. The main body of the document then provides details on 4 main eye tracking methods: electro-oculography (EOG), scleral search coils, infrared oculography, and video-based oculography. For each method, it describes the technical approach, advantages, and disadvantages. It also discusses feature-based and appearance-based gaze estimation techniques for determining gaze location from eye tracking data. The conclusion reiterates that video-based oculography techniques have various applications in research involving visual development, cognitive science,