Social Site Tags presence:
In the modern website development, it includes the general feature to share the web page content to Social media websites using features called Open Graph (Facebook, LinkedIn etc,) or Twitter Cards (Twitter)

When the content on the web page encapsulated with such Social Site Tags then it will help the website readers to make it viral to social sites using these tags. 

The check for Social Site Tags presence in the content audit will help whether the content is shareable to social media websites or not.