On wordpress it says
"Pingback the URLs in this post
When this box is checked the WordPress pingback engine will scan all of the linked URLs in your post to see if they return a XML-RPC header to indicated that they support pingback. This can slow down the posting process quite a bit so if you don't plan on using this for one particular post it's probably best to uncheck it. "
http://wordpress.org/docs/reference/post/#comments
*confused*
norra clue what it means.