As a savvy spammer, I know how to get backlinks from WordPress websites to my site. The simplest way is to comment on posts on other wordpress sites , leaving a backlink in the comment. Unfortunately, this strategy is not working well nowadays as most WordPress sites do not allow to comment any longer, or need approval before your comment can be displayed. Since you are spamming, your comments have little odd to be approved.
One day, I noticed a backlink to my site in the awstats report. I clicked that link to go to that website and found it was not an ordinary backlink. It was apparently not posted by me, and it was not in a post that was written by some guy else who took my post as reference. It is shown as a Pingback after a post on that website.
So what is a pingback and why it is shown on other websites? Well, when I wrote my post, I actually embedded a link to a post on that website in my post. When my post was published, WordPress sent a pingback to that website automatically. The owner of that website would find the pingback in the comments section after he logged in his wordpress administration dashboard. If he approved this pingback(apparently he did), a backlink to my post would be added as a comment to that post, and I got a backlink.
Similar to pingback, Trackback can also bring backlinks. Different from pingbacks, trackbacks do not need to embed a link in your post. After you edit your post, you can manually input a url (to a post on another wordpress site) in the “Send Trackbacks to:” box below the edit area(the box is not shown by default, you can display it by check on the option under the Screen Options tab). When you publish your post, wordpress will send a trackback to that url. The trackback is also shown in the comments section in the administration dashboard of the remote wordpress site. If the administrator of that website agrees, the trackback will be displayed as a comment below the remote post.
You can get more details about the trackbacks and pingbacks of wordpress here.