A peer to peer network, or P2P, allows communication between multiple networks without accessing one central network. The term is typically applied to computers sharing files among one another. For example, a person downloading a song on a peer to peer network would be downloading parts of the song from different computers at the same time, while others downloading the song would be downloading pieces from the person's computer at the same time.
There are several advantages to using a peer to peer network. If all those downloading are downloading from a single source, the source can crash and all the downloads will go down. With a peer to peer network, however, if one goes down, the download will continue from another computer that has the file. It also allows multiple people to both download and upload the same file at the same time. In a traditional setup with only one central server, the server would upload and the computers would download; the process could not run the other direction as it can in a peer to peer network.
Another advantage of the P2P network is that all participants are supplying necessary resources, such as bandwidth. Since everyone participates, the more people who show up, the more resources there are. Instead of the transfer or process slowing down as more people connect, the speed will stay the same and can even increase in speed. A central server cannot do this. If one person is downloading a song from another person, when more people with the song join, the download will go faster because it has more resources to pull from.
Disadvantages do exist in a P2P network, however. While it does allow for faster downloading and sharing, it also requires a large amount of bandwidth to support the file sharing between networks. As the technology continues to advance, P2P sharing will be possible without needing to use such a large amount of bandwidth. The second disadvantage is the potential to download or receive malicious files through the network. Since the person downloading is connecting to multiple sources, one of the sources may have a small piece of code transferred to several of the downloading computers that is intended to harm the computer or the file being downloaded.