See who a post was shared with
When someone shares a post, you can tell if it was shared publicly, privately, or with extended circles.
If a post in your stream was shared with all of Google+, you’ll see Shared publicly at the top of the post. Click Shared publicly to see more information about those who have +1’d, reshared or commented on the post.
If a post was shared privately with you, you’ll see Shared privately at the top of the post. Click Shared privately to see the profile pictures of others who can also see that content, as well as the total number of people the post was shared with.
Shared to Extended Circles
If you chose to share with your extended circles in addition to other people, clicking Extended circles at the top of the post will only show that you shared with your extended circles--specific people won't be identified.
If you'd like to notify someone of a post, just +mention them. Once they've been added, they'll be able to see the post.