Trackbacks? What are they?

Now that I’m using WordPress 1.2 I’ve noticed plenty of references to “Trackbacks” and have found very little information about what they are.

Here and here are two reasonable explanations … I’m yet to see it in action; must be time to go looking.

An associated concept are the “Pingbacks” and there is slightly more information on those here and here (official looking).

Hopefully, someone will pingback or trackback me so that I can see the effect sometime (Or perhaps I shall ping/track someone else first).