The meta description and keywords are an optional feature and have traditionally been useful for search engine optimazation (SEO). This content is not visible on your site, but can be seen by the search engines programs that index your website. The description is text which summarizes the site's content. Search engines show the meta description in search results mostly when the searched-for phrase is within the description, so optimizing the meta description can help SEO. The length of the description is recommended to be less than 155 characters. The meta keywords tag is where you put all of the keywords you use on your site. Your keywords are important – even if you take away all of the other words, they should be able to outline what your site is all about. Keywords are simply a comma separated list of words.