Trackbacks are supported in Drupal through the Trackback module. Trackbacks should be treated with care, as they basically allow anyone to place links on a blog post and therefore inviting spammers.
Trackbacks come in handy for two purposes:
- When being part of a social network of blogs, where bloggers tend to comment on each other on their respective blogs.
- For internal linking, when doing a follow up on a post. In this case, the trackback mechanism allows for easily putting a "see also" link on the original post without having to edit it.