A server is a computer used in a network and which provides a service to a client. Servers usually have more processing power, memory and storage than client computers. The client is the computer that is not acting as the server, at least at that point in time, and is requesting information or a service from the server. Understanding what a server is involves an understanding of what networks are. When computers are connected in some physical (or wireless) way and sharing services or information, this is referred to as a computer network. In a computer network, there are two or more participants where at least one of them is acting as a client and one is acting as the server.
Servers Relative To Networks
A network can be very large, called a WAN (Wide Area Network) spanning the globe, or very small as in a home or small office environment. The Internet is the largest WAN, and it depends on servers to provide connectivity and other services as well as access to shared information and applications. There are many types, categories and functions of a server, but they are always a component of a network, and networks always have at least one client and one server.
In a peer-to-peer network, each workstation (computer) serves as both client and server. The server is the computer that in that particular interaction is providing services to the client, which in that same interaction is the computer that is accessing the server's information or services. In this type of network, each computer relies on each of the other computers to provide and share its information and services. This type of network is usually only used in small offices or in the home.
In a client/server network, there is a dedicated server, which has no other function except to provide its service. In this type of network, the workstation computers are the clients. There can be more than one server providing different services, but the servers are not used as workstations. The client/server network is the most commonly used type of network.
General Server Services
The services provided by one or more servers could be as a print server, allowing and monitoring access to a printer or printers; an application server, which runs application software such as word processing or a database; a file server, which stores files for access by all of the client computers; and servers that allow and provide access to other networks, including the Internet.
Some of the most common specialized types of servers include DNS Servers, Web Servers and Mail Servers. DNS stands for Domain Name Service, and it is a server computer that holds a database of Domain Names (the human-language names used on the Web) and translates this human language name into a number address that the computer can understand and use to access the particular website. Web Servers are computers that supply access to websites, and Mail Servers provide access to email, including sending and receiving, storage and other mail services.