Meta tags, although typically unseen by visitors directly on your site, are very useful in getting them there. Title tags are only a few keywords, but description meta tags can be anywhere from one sentence, to a short paragraph. The purpose is to give search engines a summary of what your page is about.
Google specifically, offers a content analysis section as part of its webmaster tools which allows you to see if a meta tag is too short, too long, or even used too many times throughout your website. The description meta tag is placed within the <head> tag of your HTML page, the same way the <title> tag is. Do Not Forget to Close Your Tags
Although site visitors may not see these descriptions specifically on your webpage, search engines may use these descriptions as brief summaries of your page when your site shows up in search results. If there is text on your page that matches a user’s search then the search engines may not use your description meta tag.
Search engines sometimes also pull text from your sites description in the Open Directory Project – a large directory of the web edited by a community of volunteers. Since you may not know what is updated about your site in the Open Directory Project, it might be a good idea to prevent search engines from pulling this information. All in all, it’s good practice to have a descriptive meta tag in case the search engine used by your visitor can’t find text to pull.
If your meta tag gets pulled for search engine results, it would show up under the title tag and above the web link. The user’s query would show up in bold. If someone searched cupcakes, this might show up: