Event Tracking is a method available in the ga.js tracking code that you can use to record user interaction with website elements, such as a Flash-driven menu system. This is accomplished by attaching the method call to the particular UI element you want to track.
How to use it? Simply include the generated tracking event into the that last part of the link.
This refer to Google Analytics Event tracking
Example: yourdomain. com/product/promotions/onClick="_gaq.push(['_trackEvent', 'Product', 'Promo', 'FreeGifts',, false]);"