The Free On-line Dictionary of Computing (30 December 2018):

server
servers

   1. A program which provides some service to other (client)
   programs.  The connection between client and server is
   normally by means of message passing, often over a
   network, and uses some protocol to encode the client's
   requests and the server's responses.  The server may run
   continuously (as a daemon), waiting for requests to arrive
   or it may be invoked by some higher level daemon which
   controls a number of specific servers (inetd on Unix).

   There are many servers associated with the Internet, such as
   those for HTTP, Network File System, Network Information
   Service (NIS), Domain Name System (DNS), FTP, news,
   finger, Network Time Protocol.  On Unix, a long list can
   be found in /etc/services or in the NIS database "services".
   See client-server.

   2. A computer which provides some service for other computers
   connected to it via a network.  The most common example is a
   file server which has a local disk and services requests
   from remote clients to read and write files on that disk,
   often using Sun's Network File System (NFS) protocol or
   Novell Netware on PCs.  Another common example is a web
   server.

   [Jargon File]

   (2003-12-29)