Dejan Batanjac

Creates meta description write panel for posts pages and custom post types. 
Meta description write panels are not present in the default WordPress installation.
Meta description were traditionally important for website SEO. Today, with the improvement of the software that reads and summarizes the textual documents, they are loosing the importance.
Still you can find them useful on pages with low or even no text.

SEO Meta Description

Creates meta description write panel for posts, pages and custom post types.

Aby Rafa

Show meta description in your homepage, single post and page. This plugin helps you to attract visitors and boost traffic. Just plug and play. (WordPress Simple SEO – Meta Description).
If you want to know how this plugin works, right click on your page and then select view page source. You will see your meta description between the header tag.
<ul>
<li><a href="http://wp.labnul.com/plugin/one-meta-description/" rel="nofollow ugc">Plugin Homepage</a></li>
</ul>

One Meta Description

Show meta description in your homepage single post and page. (Wordpress Simple SEO - Meta Description).

SEO Meta Description vs One Meta Description