Dictionary.net

A common form of distributed system in whichsoftware is split between server tasks and client tasks.A client sends requests to a server, according to someprotocol, asking for information or action, and the serverresponds.This is analogous to a customer (client) who sends an order(request) on an order form to a supplier (server) whodespatches the goods and an invoice (response). The orderform and invoice are part of the "protocol" used tocommunicate in this case.There may be either one centralised server or severaldistributed ones. This model allows clients and servers to beplaced independently on nodes in a network, possibly ondifferent hardware and operating systems appropriate totheir function, e.g. fast server/cheap client.Examples are the name-server/name-resolver relationship inDNS, the file-server/file-client relationship in NFS andthe screen server/client application split in the X WindowSystem.Usenet newsgroup: news:comp.client-server.["The Essential Client/Server Survival Guide", 2nd edition,1996].