Pingbacks are automatic notifications added (as a kind of comment) to posts you link to in your articles. Whether a visitor is reading something way back in your archives or your most recent post, the pingbacks makes sure she can easily find any follow ups.
This is great for keeping related articles together, but private blogs are forced to disable Pingbacks to avoid notifying other sites when linking to them!
“Only Self Pings” solves this by only allowing pings to your own site (and whatever URLs you add to the whitelist).
Additional Notes
Copyright (C) 2012 Ulf Benjaminsson (hello at my full name dot com).
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA