Server

Basically, a server is a networked computer that listens for service requests from clients, and provides responses to legitimate requests. Almost all Internet services are delivered by networked computers that run specialized server software, typically at least one program or process for each such service that a machine can deliver. Thus, the computer that delivers Web pages can be called a Web server (though it may serve other things as well), while the machine that delivers Telnet services can be called a Telnet server.

W3E References:

client/server

daemon

Web server

Detail:

A network server provides the core functions for supplying services to network users and providing management, access, and control functions for network administrators. Generally, basic network server functions include:

• Storage of operating system information, including command and service handling capabilities.
• Storage of user programs and data, such as those needed to supply Internet services to end-users.
• Management functions for the file system.
• Management functions for security and user access, including partitioning available information between what's public (and available via Internet access) and private (which typically requires password and account level access privileges to see and use).
• Network monitoring and management components.
• Data protection functions for reliability and availability, to make sure the server is always accessible when needed (servers typically require bigger, more robust machines and capabilities than do the computers on the average user's desktop).

Most Internet servers are members of a server category called "dedicated servers"--that is, they're dedicated to the job of providing one or more Internet services and little if anything else. This is particularly true for servers available to the entire Internet, because of potential demand and usage requirements.

The most common operating systems used for Web servers today include:

• Some variety of UNIX (about 70%)
• The Macintosh (typically a Quadra class machine or a PowerPC Mac, running MacHTTP or some variant thereof; about 10%).
• Windows NT (about 5%).
• Other (the remaining 15% is a grab bag of all kinds of machines, from mainframes to PCs running Windows 3.X, Windows 95, or something even stranger).

Source: The Web Survey conducted by NetWizards and Virtual Library statistics.