A trackback is an automated process of notifying a blog that your linked to an article. When another blog is being referenced in a blog post, the trackback field can be used to initiate a process that 'pings' the other blog, alerting it to the incoming link.
Not all blogging software supports trackbacks, and some require trackbacks to be verified before they will show up on the blog.
Why Should I Send a Trackback?
Trackbacks are a great way of letting another blogger know that you are referencing their work. Not only is this common courtesy, it might also lead to that blogger creating a link to back to your blog in a future article.
Trackbacks are also displayed in the comments section. This allows readers to easily find other blogs that have written on the same subject, thus it can provide some incoming traffic.
They are also good for search engine optimization (SEO). Every incoming link helps with SEO, so both sides are getting a little boost from the link and the trackback.
How Do I Send a Trackback?
Unfortunately, there is no standard address for trackbacks. So, to send a trackback, you will need to check the comments section of the blog article. If it supports trackbacks, it will usually have a trackback URL. It is important to use the trackback URL and not the linkback URL, which is the address of the article itself.
The most common address for trackbacks is the web address of the article with "/trackback" at the end.