The OG image will be downloaded to your site and set as Featured Image of the newly created post.
From ogp.me:
The Open Graph protocol enables any web page to become a rich object in a social graph. For instance, this is used on Facebook to allow any web page to have the same functionality as any other object on Facebook.
Translations: Português – Español.
Released under GPL, you can use it free of charge on your personal or commercial blog.