UPNP is essentially plug-and-play discovery of network devices using XML over HTTP over UDP. It is relevant because it will be able to automatically open up incoming ports in NAT’s soon, which is relevant to the p2p community.
Check out UPNP Evangelism to learn about it.
I got this powerpoint file from http://www.upnp.org/resources.html and I tried to put it in a more usable html form. This is the evangelism document intended to get people excited about UPNP as well as educate them.
The powerpoint is also available UPnP_Device_Architecture_Generic_20000710.ppt
