Web_server

A Web Server is a software application that uses the HyperText Transfer Protocol. A Web Server is usually run on a computer that is connected to the Internet. There are many Web Server software applications, including public domain software from Apache, and commercial applications from Microsoft and Oracle. A Web Server may host or provide access to Content and responds to requests received from Web browsers. Every Web Server has an IP address and usually a domain name, eg. www.murdoch.edu.au or a sub-domain, eg. www.it.murdoch.edu.au. Some Web Servers are Virtual Servers.
 

Let's say that you are sitting at your computer, surfing the Web, and you get a call from a friend who says, "I just read a great article! Type in this URL and check it out. It's at http://computer.howstuffworks.com/web-server.htm." So you type that URL into your browser and press return. And magically, no matter where in the world that URL lives, the page pops up on your screen.
At the most basic level possible, the following diagram shows the steps that brought that page to your screen:
Your browser formed a connection to a Web server, requested a page and received it.

Clients and Servers
In general, all of the machines on the Internet can be categorized as two types: servers and clients. Those machines that provide services (like Web servers or FTP servers) to other machines are servers. And the machines that are used to connect to those services are clients. When you connect to Yahoo! at www.yahoo.com to read a page, Yahoo! is providing a machine (probably a cluster of very large machines), for use on the Internet, to service your request. Yahoo! is providing a server. Your machine, on the other hand, is probably providing no services to anyone else on the Internet. Therefore, it is a user machine, also known as a client. It is possible and common for a machine to be both a server and a client, but for our purposes here you can think of most machines as one or the other.