Definition: a meta tag hidden in the HTML that describes the page’s content. Should be relatively short; around 12 to 20 words is suggested. The meta description provides an opportunity to influence how your Web page is described in the search results, but it will not improve your search rankings. Make sure your meta description reflects the page content or you may be accused of spamming
FirstClickSEO Commentary: This is also the copy that appears on the search results. It should be simple and catchy.