When a shared message appears in the stream, the post will come from the person that “shared a message” and indicate the group name if it was shared with an individual group. The original post is indented and includes the original author, where it was posted, and the body of the message, including text, links, and attachments.
A share indicator appears on the original message (arrow icon) and shows the number of times the post has been shared publicly. Clicking the Share hyperlink above the Write a comment text box of the original message shows you a list of people who shared the message.
When you search the community for a message that has been shared, the search returns both the original message and shared message as results.