A server is a computer program or device that provides services or resources requested by other programs or devices, known as clients. This pattern of connecting a server to a client over a network or a device is known as the client-server model.

A server may have many clients at once, or a single client can use multiple servers. Servers also offer a variety of functions, ranging from website and web application hosting, to providing shared disk access, printer connections, and database services.

The word "server" can refer to either a physical machine (such as an Ubuntu server) or to a service provided to clients (such as an OpenVPN server or an Apache web server) being provided to clients.

To learn more about server setups and processes, check out the following tutorials:

-5 Common Server Setups For Your Web Application

-Sysadmin eBook: Making Servers Work