Although one of the old meta tags — they keyword tag — has pretty much gone the way of the dinosaur, the meta description tag still has value. Although Google and other search engines don’t really give the tag much (if any) weight when it comes to determining the rank of your page, they’re still displayed in the search results. At least sometimes.
Google generally will display a page’s description content (or at least some of it) underneath the underlined (title tag) link in the results listings if it’s deemed to be "informative" enough. In Raj Krishnan’s post, "Improve snippets with a meta description makeover" on Google’s Webmaster Central Blog, he says the title and description tags should "accurately represent the web result" and give "users a clear idea of the URL’s content." Fair enough.
If your description tag is just a bunch of keywords, it’s less likely to be shown in the search engine results pages. Also, it’s best if the tag is not automatically generated, but rather "human-readable and diverse."
If you have any control over the page, and want to increase the likelihood of click-through from search engine listings, try to input a useful and descriptive description tag.