The primary characteristic of a peer-to-peer (P2P) network is its decentralized structure, where each participant (peer) acts as both a supplier and consumer of resources. Unlike traditional client-server models, P2P networks allow direct communication and sharing of data between users without requiring a central server. This architecture enhances efficiency and resilience, as it can adapt to fluctuations in network size. P2P networks are commonly used in file sharing, collaborative applications, and cryptocurrency systems due to their scalability and reduced reliance on centralized infrastructure.