Trackbacks are another popular blogging tool. A trackback is often used instead of a comment. A reader who owns their own blog may write something about a post they have seen on your blog network and send a trackback to the relevant blog owner using the trackback link. The trackback then appears as a comment with a link back to the post the reader wrote on their blog. Trackbacks look just like normal comments, except the text contains a short excerpt from the blog post that the trackback was sent from:
WordPress MU supports trackbacks by default; blog owners can send a trackback by pasting the correct trackback link into the Send Trackbacks box on the Write Post page. Trackbacks can be sent at the time of posting or by using a cron job that sends all pending trackbacks in one go.
To accept trackbacks, you will need to make sure that the option Allow link notifications from other blogs is ticked on the Discussion Settings page.