You know what an elevator pitch is right? Its the critical 30 seconds or less you have to sell an idea to someone.
Meta descriptions are the equivalent of an elevator pitch for each one of your pages exposed to search engine result pages. They are the 156 characters that appear below each page indexed by the search engine machines.
Research shows that only 20% of all web pages contain these important meta tags in their HTML and over 85% of these websites are unfit to be submitted to the search engines. Here you will find a treasure trove of material to help you make good meta tags so that your site is found on the internet, as high in the search results as possible.
The big three search engines are cagy on whether SEO affects ranking, google more so than the other two. There is much debate by SEO aficionados whether you should even use them with some supporting the view they can be used by competitors to figure out what key words you use.
I support the use of them as a tool for grabbing your potential customers attention so they click through to you and not your competition.