The Server is Part of the Client–Server model. In this model, a Server Serves Data for Clients. The Nature of communication between a Client and Server is Request and Response. This is in Contrast with Peer-to-Peer Model in which the Relationship is on-Demand Reciprocation. In Principle, any Computerized Process that can be used or called by another Process. (Particularly Remotely, Particularly to Share a Resource) is a Server, and the Calling Process or Processes is a Client. Thus any General Purpose Computer Connected to a Network can Host Servers. For example, if Files on a Device are Shared by some Process, that Process is a File Server. Similarly, Web Server Software can Run on any Capable Computer, and so a Laptop or a Personal Computer can Host a Web Server.
Client–Server Systems are Today Most Frequently Implemented by (and often Identified with) the Request–Response model. a Client Sends a Request to the Server, which Performs Some Action and Sends Response Back to the Client, Typically with a Result or Acknowledgement. Designating a Computer as “Server-Class Hardware” Implies that it is Specialized for Running Servers on it.