What is the difference between Pingback and Trackback
The fundamental difference, in terms of WordPress, is that, with Pingbacks, the receiving system automatically verifies that the sending system does in fact link to it. This is important because Trackbacks are not system verified and are therefore open to comment spam. It is possible to send a Trackback from a post without any link to the receiving system whereas it isn’t possible to send a Pingback to the receiving system without having a link (and, with Pingback, the receiving system automatically verifies whether a link exists).