How P2P netork work?

A pure peer-to-peer network does not have the notion of clients or servers, but only equal peer nodes that simultaneously function as both "clients" and "servers" to the other nodes on the network.

The P2P model creates the effect of communal living. Imagine a group of thirtysomethings with common ideas about living together and sharing certain belongings. They have one cabinet where they put everything they're willing to share—clothes, CDs, food—but they can also have a locked cabinet where they store private belongings—diaries, savings bonds, photos. P2P works the same way. By downloading various types of software onto a hard drive, you can connect to a network of other users who have downloaded the same software. You specify which information on your hard drive you want to make public, and you can access what others have made public. So if you're looking for a photo of some special Olympic moment, and it's available on any of the hard drives of the connected computers, it's all yours.