Event Tracking is a feature of Google Analytics you use to track different actions visitors take on your website, such as clicking a button or downloading a file. It is useful for tracking actions on your website that don't take the user to a new page (such as clicking play on a video player).
For e.g. here’s how to track a "Pause" button on your video, by attaching the following call to the "Pause" button on the video player for the Snoopy movie: pageTracker.trackEvent("myVideos", "Pause", "Snoopy");
When users click the "Pause" button for the Snoopy movie, an event for that category/action combination is triggered.