The terms pingbacks and trackbacks are used almost interchangeably, and are pretty much the same thing on the surface. They actually utilize different technologies and originated for different purposes, but these days they are becoming more intertwined. I’m just going to call them trackbacks for the purpose of this post.
What are they?
Essentially both are forms of notifications or communications between blogs.
For example, if I write a blog post and in it I link to a blog post on another site, an excerpt of my post containing the link will show up on that blogger’s site in their Comments section, along with a link back to my post. Since trackbacks are handled through comments, the blogger gets to moderate it like any other comment. So he/she will be able to see that I referenced their blog and if they approve the comment I now have a link from their site to mine. This is a trackback.