its a program that will let you connect to others PC around the world and download files off of their hard drive. If you put P2P into a search engine like google then it will come up with a few good ones but be warned it may be safer than downloading things off of websites but you can still get alot of viruses off the P2P progs aswell, Progs like kazaa get a bad rep for having lots of viruses on there but i dunno.
You could also try out bit torrent downloads, you just download the software, go onto sites for them, download a little file an d then open that file up into the software which will connect you to the real download.
i am not an expert so i sujest that you try and look up these progs on wikipedia.com for moreinfo on the subjects.