These icons represent items in the HTML code, including comments, browser title, meta tags and keywords. You can look at the code by clicking on the icon and looking in the Properties Inspector. All are important to making sure your index.html file is indexed properly by search engines, bringing users into your site properly. Select this text in the Properties pallette and change it to something appropriate. If it's the top index file in your site, it can be as simple as the name of your department or division.
Extra words are ok, as they help search engines find the site.
Click the icon for description. Select this text and type in your own description of the site. Can be up to a couple of hundred words long. This also helps search engines. Select this text and type in your own keywords.