This entry was published at least two years ago (originally posted on March 24, 2003). Since that time the information may have become outdated or my beliefs may have changed (in general, assume a more open and liberal current viewpoint). A fuller disclaimer is available.
I’ve tried to explain TrackBack in the past when asked, though I’ve never been too sure how well I did. Handily enough, I don’t have to try anymore, as Ben and Mena Trott — the creators of MovableType — have written A Beginner’s Guide to TrackBack. Good stuff!