An event is a user interaction with a web page element like videos or external links. GA can’t track such events by default as they don’t generate pageviews when they occur. You can set up event tracking in GA by calling _trackEvent() method each time the user interaction you want to track occurs. Read more: http://www.seotakeaways.com/google-analytics-setup-checklist/#ixzz2SL2qWy1O
All sites that implement Google Analytics are required to have a privacy policy somewhere on the website (as per Google's Terms of Service). This policy must indicate that the site uses a cookie to collect anonymous traffic data.