2.1. Resource-centric addressing for unstable environments

Peer-to-peer is a class of applications that takes advantage of resources—storage, cycles, content, human presence—available at the edges of the Internet. Because accessing these decentralized resources means operating in an environment of unstable connectivity and unpredictable IP addresses, peer-to-peer nodes must operate outside the DNS and have significant or total autonomy from central servers.

That's it. That's what makes peer-to-peer distinctive.