The document discusses the roles of computers in a network as peers, clients, or servers. It also describes different network models including peer-to-peer networks (workgroups), server-based networks (domains), and hybrid networks. Peer-to-peer networks have no central server and every computer is a peer. Server-based networks divide tasks between servers that provide services and clients that request them. Hybrid networks contain elements of both peer-to-peer and server-based networks.