Tracking back

The best way to understand trackbacks is to think of them as comments, except for one thing: Trackbacks are comments left on your blog by other blogs, not by actual people. Although this process may sound mysterious, it’s actually perfectly reasonable.
A trackback happens when you make a post on your blog and, within that
post, you provide a link to a post made by another blogger in a different
blog. When you publish that post, your blog sends a sort of electronic
memo to the blog you linked to. That blog receives the memo and posts an
acknowledgment of receipt in a comment within the post that you linked to
on their site.
That memo is sent via a network ping (a tool used to test, or verify, whether
a link is reachable across the Internet) from your site to the site you link
to. This process works as long as both blogs support trackback protocol.
Trackbacks can also come to your site by way of a pingback — which, really,
is the same thing as a trackback, but the terminology varies from blog plat-
form to blog platform.
Sending a trackback to a blog is a nice way of telling the blogger that you
like the information she presented in her blog post. Every blogger appreci-
ates the receipt of trackbacks to their posts from other bloggers. Figure 5-3
shows one trackback link, below the Who’s Linking Here header.