The term "server" is derived from "to serve".
Servers manage the network and are junctions within the Internet. Servers are central computers in a network which provide work stations/clients with data and resources. A server can consist of a computer including the corresponding operating system and utility program. Or a server can be just a program providing certain services like DNS or web service.
There are different server classes for different tasks including:
Database server: Provides clients with databases and space on the database system and backs up user databases.
Application server: Allows users to access one or several applications.
Database server: Includes a database. The server's task is to manage and organize data and to insert, sort and search at high speed for data records.
Compute server: Offers great computing power, e. g. Cray at institutes for nuclear research.
Internet server: Provides internet and intranet services, e.g. World Wide Web, Domain Name Service (DNS), FTP or e-mail.
Media server: Provides multimedia data (e. g. audio and video clips) in real time and top quality.