Trackbacks are notifications from your WordPress site that another website has linked to you. The trackback notification you get will ask you to ‘Approve It’, ‘Trash It’, or ‘Spam It’. The message typically looks like this…
“A new trackback on the post [your post url] is waiting for your approval”
If you approve it, WordPress will add a comment to your post linking back to the other site. This may or may not be a good idea – if the website is reputable, then it might be a good idea to link back to it letting your visitors know that the site links to you. If it is clearly a spam attempt, then click the ‘Spam It’ link in your email. Otherwise, just ‘Trash It’.
You can elect not to be notified of trackbacks by going to your ‘Settings’->’Discussion’ in your WordPress dashboard, and then unchecking the ‘Pingbacks and Trackbacks’ option.