Example: "The blog entry currently has five trackbacks that link to it."
Trackback is a protocol for notifying websites that other websites have linked to it. When a trackback link is added to a Web page, the linked website is notified that the link has been added. However, both websites must support the trackback protocol in order for the system to work. For this reason, trackback is most commonly used by blogging websites to share links and responses to blog entries.