This is a great feature that truly makes sense to users. Here you are surfing the web and you want to share the information in that moment, however, you only want a certain group of folks to view this new online content that you found. Why? Because it only applies to that specific group thanks to the circles that help filter your own data sharing. Moreover, the snippets will make your content look more visually appealing as well like the way Facebook allows a user to share links with thumbnails.
You can learn more about it in this video or read the official Google announcement here: