Meta descriptions do not help with ranking your website on search engines but can help with increasing the click through rate. Meta descriptions are placed within the head tag and should not exceed 165 characters. Meta descriptions do not show up on your page and are only used to show up on search engines. Google may sometimes replace your description with a snippet of text from your page so you should not spend too much time on this.
If you click on the Search Appearance tab on the side bar of GWT, you’ll see a link for HTML Improvements.
HTML Improvements shows you which meta descriptions, title tags and non-index-able content needs to be addressed by the webmaster to improve the site’s user experience and performance.
In the sample data above, there are 233 duplicate meta tags and 33,224 duplicate title tags that should be addressed for this website example.