Description of a post on facebook?

If I post a link on the facebook page it automatically loads up the information in the page such as featured image etc. but I noticed that the image is loaded with the title but the description isnt loaded instead related posts are. Content of the post is not loaded as in its invincible to facebook. This got me into thinking if the content is invincible to crawlers as well. Any idea on how to fix it and whats gone wrong?