A server is a computer on a network that listens for requests from other computers, often called clients, and responds to them. Common types of servers include web servers that deliver webpages, file servers that store files, print servers that manage printing tasks and database servers that store organized sets of information. Servers can run on independent computers, or server software can be run on a computer that's also being used for other work.
What Is a Server?
Computer scientists sometimes talk about the client-server model of networking, where a system is either a client requesting that another system return data or perform computation, or a server providing the answers to a client's request. A server can be located in an office, in a dedicated data center or, in the case of home servers, simply in the corner of a home office or living room.
In some cases, certain computers function entirely as clients, outsourcing almost all work to server systems. Low-powered machines that have such a role are sometimes called thin clients. Computers on the World Wide Web are usually strictly either clients or servers. Although it's possible to access a website from a server or to serve up content from a home desktop or laptop, it's not particularly common.
In other cases, a computer may operate as both a client and a server in various scenarios. For example, it's common for a web server to receive a request from a client and then, in response to that request, send a query to a separate database server, essentially becoming a client itself.
While some servers may have specialized hardware, many servers today run server software on top of standard operating systems such as Linux or Microsoft Windows. That software handles requests from clients and is essentially what turns the computer into a server.
Internet and Web Server Software
One of the most common types of servers is the web server. This type of server handles requests from browsers such as Google Chrome or Mozilla Firefox across the internet or on a local network and responds with webpages, images and other data requested by browsers.
Common web servers include the open-source projects Apache and Nginx and Microsoft's proprietary software called Internet Information Services, or IIS. Some companies built their own web servers for their own use to handle their own unique traffic loads or other needs. Many organizations use web servers in conjunction with other types of technology, such as load balancers to distribute tasks between computers and content distribution networks, or CDNs, that store and speedily get material to users.
Understanding Database Servers
Many organizations also rely on database servers, which store information in reliable and speedy ways that make it easy to update and access. Common database server products include Microsoft's SQL Server, PostgreSQL and MySQL.
Many database servers, including those, communicate with database clients using variations on the structured query language, or SQL. This specialized programming language is designed for requesting and editing data in a potentially large database, and it can be written directly by programmers or generated by other software.
Database servers are used for everything from storing corporate accounting records to holding blog posts on systems attached to popular web servers.
File and Print Servers
File and print servers are two types of servers commonly found on an office network. A file server stores files in a place where they'll be accessible by multiple users, usually with some security settings, and a print server communicates with printers and with other computers to manage printing documents.
Both can be run on stand-alone computers or on computers also being used for other office work.