Web Server:

• It is a server used to communicate with Web Browsers as its clients and the communication protocol used in this case is HTTP (Hyper Text Transfer Protocol). This is why a Web Server is also called an HTTP Server.
• The primary function of a web server is to store, process and deliver web pages to clients. The communication between client and server takes place using the Hypertext Transfer Protocol (HTTP). Pages delivered are most frequently HTML documents, which may include images, style sheets and scripts in addition to text content.
• Every Website sits on a computer known as a Web server. This server is always connected to the internet.
• Every Web server that is connected to the Internet is given a unique address made up of a series of four numbers between 0 and 255 separated by periods. For example, 68.178.157.132 or 68.122.35.127.
• On a web server, the HTTP server is responsible for processing and answering incoming requests.

1. On receiving a request, an HTTP server first checks whether the requested URL matches an existing file.
2. If so, the web server sends the file content back to the browser. If not, an application server builds the necessary file.
3. If neither process is possible, the web server returns an error message to the browser, most commonly "404 Not Found".

How web servers work?

Whenever you view a web page on the internet, you are requesting that page from a web server. When you type a URL into your browser (for example, "https://www.quackit.com/html/tutorial/index.cfm"), your browser requests the page from the web server and the web server sends the page back:

The above diagram is a simplistic version of what occurs. Here's a more detailed version:

1. Your web browser first needs to know which IP address the website "www.quackit.com" resolves to. If it doesn't already have this information stored in it's cache, it requests the information from one or more DNS servers (via the internet). The DNS server tells the browser which IP address the website is located at. Note that the IP address was assigned when the website was first created on the web server.
2. Now that the web browser knows which IP address the website is located at, it can request the full URL from the web server.
3. The web server responds by sending back the requested page. If the page doesn't exist (or another error occurs), it will send back the appropriate error message.
4. Your web browser receives the page and renders it as required.

• A web administrator maintains web server services (such as Apache or IIS) that allow for internal or external access to web sites. Tasks include managing multiple sites, administering security, and configuring necessary components and software. Responsibilities may also include software change management. They mainly deal with the following : Although tasks can overlap with other areas of web development in small organizations, pure web administration positions would cover the following:
• Administration, installation and maintenance of web servers
• Selection of appropriate web server platform and operating system - Which web server should the company use – Apache or IIS? Should it be hosted on a UNIX, Linux or Windows box? When should the company upgrade to a new version of the web server software? The web administrator has to make these calls.
• Advice on the selection of web development tools - Gives assistance to the web publishing group during the selection of web development tools (Dreamweaver, FrontPage, GoLive, etc.).
• Ensure routine back-ups of the web servers occur.
• Prepare and implement disaster recovery plans - Fire, flooding, theft, security breaches and equipment failures can all lead to loss of data and systems capabilities. Customers normally expect a web site to be operating and available 24/7. Having a plan to smoothly and efficiently recover from failures is essential.
• Generate web site statistics reports - Upper management, web publishing, sales, marketing, accounting and fulfilment will all be interested in how users are using your web site. This information is invaluable when deciding how to update your site and which areas are the most popular.
• Ensure security is adequate on the web servers - There will always be nefarious or inquisitive individuals attempting to breach your site.
• Evaluate new hardware and software for possible adoption at your company.
• Maintain connection to the Internet - This includes negotiation with third party ISPs and telecommunication companies to provide needed bandwidth and connectivity.
• Maintenance of user accounts - Content on a web site or intranet is not necessarily available to everyone. Individual user accounts must be created to give appropriate personnel access to the information they need.