Web search engines describe and index Web pages when generating a search list, using the first lines of text found on a Web page as a page description. Attaching a meta tag to a Web page—an HTML tag that describes the content of the page—gives you control over what text a search engine uses, thus preventing your page from being described incorrectly. By ensuring that your Web page is properly described and indexed on a search list, Web users will be able to find your site more readily in a search, and you will generate more traffic to your site.
The various categories and options used in meta tags come from the data-transfer system and organization used by Web servers. In QuarkXPress, meta tag categories are organized into a meta tag set, which in turn can be incorporated into the code for a Web page. It's all behind the scenes, though; meta tags don't produce any visible items on a Web page.