What is A Meta Description tag?
The description meta tag can be seen as an extension of the title but is not as relevant for the search engines as the title tag. The description holds up to 160 characters including whitespace, the limit for Google, and should be relevant to page content.
A common recommendation of how to write a good description is to use secondary keywords for the page content.
Good descriptions gives more visitors
A well written description does not only build relevance but also increases your chances of getting the visitor to click through to your site - even if it is not as important as a well written title. People tend to click on the links that have both informative titles and descriptions. Use it to your advantage.