Server

A server is a computer program or device that accepts and responds to requests made by another program, known as a client.

A good comparison is a customer (client) who orders a packaged which is delivered by the postman (server).

Servers are used by software applications and website to manage network resources including to control access to a network, e-mail services, host a website or store large amounts of data securely for quick access as required.

Some of the most common server types are:

• A Web server is a computer program that serves requested HTML pages or files. In this case, a Web browser acts as the client.
• An application server is a program in a computer in a distributed network that provides the business logic for an application program.
• A proxy server is software that acts as an intermediary between an endpoint device, such as a computer, and another server from which a user or client is requesting a service.
• A mail server is an application that receives incoming e-mails from local users (people within the same domain) and remote senders and forwards outgoing e-mails for delivery.
• A virtual server is a program running on a shared server that is configured in such a way that it seems to each user that they have complete control of a server.
• A blade server is a server chassis housing multiple thin, modular electronic circuit boards, known as server blades. Each blade is a server in its own right, often dedicated to a single application.
• A file server is a computer responsible for the central storage and management of data files so that other computers on the same network can access them.
• A policy server is a security component of a policy-based network that provides authorization services and facilitates tracking and control of files.