Trackbacks are a method of linking conversations and articles between blogs that is both automatic and extremely powerful. When an author writes an article that discusses the entries on an alternative blog, his software automatically sends a ‘ping’ to the other blog. If this blog is also Trackback enabled it will be able (at the author’s discretion) to display a link back to the linking site and a summary of content.
Starting with Moveable type and developing as part of other blogging and content management systems such as WordPress these pingbacks and trackbacks have become an important way for bloggers to notify each other of links and share content. They have also become a tool for spammers who would look to manipulate trackbacks with fake pings and such techniques.