Trackback is a system used to associate posts on different blogs and, in a greater sense, it allows blogs to “share” readers.
An example! Just as a simple example of how Trackback works: If you have just posted an article discussing Admiral Byrd’s second Antarctic expedition and then happen to run across a similar or related post on another blog, you could use the trackback mechanism to notify the other poster of the existence of your post. When your trackback notification (which is the permalink to your post and, possibly, some basic information about your blog) appears on the post in the other blog that blog’s readers will also be notified that you have something to say on the subject and they may pay you a visit.
Everyone can have it but not everyone does! Some blogs have this Trackback capability built in and others do not but the good news is that Haloscan, a very popular comment tracking program, now offers a trackback feature for those who don’t have it and the better news is its FREE! If you are interested you can go to http://www.haloscan.com/members/join.php to sign up. Note that signing up for Trackback (if you don’t already have it) will give YOU a trackback capability but you will still not be able to Trackback to a post on a blog that does not have Trackback.
Trackbacks vs. comments! Normally you will see a post you have something to say about and comment on it. Using a Trackback when you don’t have an honestly related post — one that adds something relevant or clarifies the subject post — is not an accepted practice. If you become known as a “trackback spammer” by sending unrelated trackbacks you may be banned from the offended blogs.
How it works! Trackback works by sending a “ping” (an electronic notification) from your blog to another blog to notify them of your post. This ping also notifies their Trackback program to list your post. Some bloggers moderate their trackbacks, i.e., they manually review each trackback notification and verify that it is indeed a related post — this prevents spammers from relating their junk posts to real blogs. If the blogger reviews your post and finds it relevant he or she can permit the trackback and your post will then be listed as a trackback on the other blog.
The first step in creating a trackback is getting the “Trackback URL” from the post where you want to send your Trackback notification. If the post does not have a Trackback URL, they either don’t have a Trackback capability or they have it turned off.
Next, copy that URL into the appropriate place on your blog’s post. This will usually be identified by some reference to “Trackback URLs” or “Trackback pings.”
Next, republish your blog — your trackback software will automatically send the Trackback ping to the target blog’s post.
That’s all here is to it, your trackback, featuring a permalink to your post, will be sent to the target post and, after being approved (if the blogger is moderating trackbacks) your Trackback will be listed.
Other functions! On some systems it is possible to send simultaneous Trackbacks to more than one target posts. Another capability of Trackback allows you to send a trackback ping to yourself, linking a post on another blog — this lets your readers know that the other post is out there and can be considered a “recommended reading” type function.
Just a review of four important Trackback points!
Not every blogger has a Trackback capability and some that have it do not have it enabled.
Some bloggers moderate their trackbacks to avoid unrelated posts being linked. Some however do not moderate or even monitor their Trackbacks, so trackback spammers can sneak in. Don’t be a Trackback spammer and don’t tolerate them.
Haloscan is now offering Trackback capability packaged with their commenting program (both are free).
Installing Trackback on your blog will not allow you to send Trackbacks to blogs without that capability.
More information on Trackbacks! Wikipedia has a very comprehensive entry on Trackbacks you can find it at: http://en.wikipedia.org/wiki/Trackback. Wikipedia articles are always comprehensive and will provide you with information you can rely on.