A server is software or hardware offering a service to a user, usually referred to as client. A hardware server is a shared computer on a network, usually powerful and housed in a data center. A software server (often running on a hardware server) is a program that provides services to client programs or a user interface to human clients.
Services are provided generally over local area networks or wide area networks such as the Internet. A client program and server program traditionally connect by passing messages encoded using a protocol over an API.
- An Internet-connected Web server is sending an HTML file to your browser software so that you can read this page
- Local area network server for file, name, mail, print, and fax
- Minicomputers, mainframes, and super computers at data centers
There are also Virtual Servers used by Cloud Computing Providers e.g. an AWS EC2 Instance from AWS.