What is the Google AdSense preview tool?

What is the Google AdSense preview tool? : "The Google AdSense preview tool is an addition to the right-click menu for Windows Internet Explorer 6.x, allowing you to preview the ads that may show on any web page. With just a few clicks, you can see what ads may appear on your new web pages, or make an educated decision on whether to add AdSense to your existing site pages. "