Meta description tag plays vital role on driving your site(s) traffic from search engines. It gives descriptions of the page's contents accurately, search engine grab description as a short resume of your page content. And with an algorithm that I myself don't even know how it works, search engine put your page on a result page .. thanks to this awesome meta description.
Wordpress have an 'add meta tag' plugin, to put your meta tag (not only decription, it could be keywords or some others) on your post.
But how can I put meta description (which are varying from page to page) in blogspot?