Google can actually display whatever it likes in the search results i.e. what it thinks is relevant to the most common queries about that page/site/file/whatever but most often it goes with whats in your meta title and meta description tags e.g.
Daily Telegraph Google Result
Corresponding meta tags
<title>News - Latest breaking news - Telegraph</title>
<meta name="description" content="Latest news, breaking news and current news from the UK and around the world, plus celebrity news and political news from Telegraph.co.uk, all the latest breaking stories" />
So you need to insert these two meta tags into the
<head></head> section of each of your HTML pages, it is best to have unique content about each page in them, rather than the same text repeated over and over again.
@Joshak's answer shows exactly where this particular description is coming from and how to change it on DMOZ, my answer tells you how you fix your site.
I would also recommend implementing google webmaster tools as it will help alert google to the changes to your page and give you a better idea about what google knows about your site.