I've never really understood the differences between "pingback" and "trackback".
Google likes to display older articles, which has interesting effects The first thing that I found that tried to explain the differences was published more than 3 years ago and has way more detail than I want. But this whitepaper led me to more resources on pingback and trackback.
If I can summarize:
Pingback * Just ping a blog (or whatever) with your own blogging software * No detail about what you said about them * Receiver doesn't link back to you
Trackback * Details about what was said * Receiver can link back if they want.
SixApart has a trackback technical doc that explains more.