Server is the general name for process or system which provides some service. The service is usually provided by some of application network protocol, for instance HTTP (web server) or LPD (print server). Process which uses the service is called client; architecture which uses this principle is called client-server. By the name server there is called also the computer (hardware) which provides these activities.
Servers are used there where is need of services for other PC in network.
Almost the entire structure in the internet is hidden behind the client server. Many millions of servers located all over the world are interconnected and thus form the net. The numerous services that are provided by internet servers include: Web, DNS (Domain Name System), electronic mail, transfer of files, audio and video, on-line games and many more. Virtually any action performed by an internet user expects one or more counter-actions from one or several servers.
Some of server types:
Web server – provides WWW pages for a file server especially in the Internet network - is used as a central database of data (documents) for example in corporate networks
Database server – is used for storing structured data (databases), enables searching.
Proxy server – provides for other users’ access to another network (e.g. the Internet)
Print server – is used to make the services of a printer available for other users of the network
Application server – a computer specialized in the operation of an application
Gaming server – offers multiplayer games
OSI Referential Model
If computers of different hardware platforms and different operating systems are to communicate with one another in a network, they must use the OSI model.