Mosey – See the pingbacks below your comment on this page? Those are pingbacks. They happen whenever a blog that supports pings or trackbacks (like WordPress, or Typepad and many other blog engines, *not* Blogger or most photoblog software AFAIR) mentions another post. The blog sends a “ping” to tell the other post, “I mentioned you! Add this to your comments please!”
It’s a great way of keeping a conversation going, especially across separate websites. Check the two pings below for posts about moving your blog!