Pretty much the same thing, the links above explain what they are for…
I’ll quote this section from link 1…
Function
A trackback is an acknowledgment. This acknowledgment is sent via a network signal (ping) from the originating site to the receiving site. The receptor often publishes a link back to the originator indicating its worthiness. Trackback requires both sites to be trackback-enabled in order to establish this communication. Trackback does not require the originating site to be physically linked to the receiving site.
Trackbacks are used primarily to facilitate communication between blogs; if a blogger writes a new entry commenting on, or referring to, an entry found at another blog, and both blogging tools support the TrackBack protocol, then the commenting blogger can notify the other blog with a “TrackBack ping”; the receiving blog will typically display summaries of, and links to, all the commenting entries below the original entry. This allows for conversations spanning several blogs that readers can easily follow.