• A web application is a computer program that utilizes browsers and web technology to perform task over the internet.
• Web applications use a combination of server side scripts (PHP, ASP) and client side scripts (HTML, CSS, JavaScript).
• Server side scripts are used to handle the storage and retrieval of information from database.
• Client side scripts are used to present information to users.
• Web app helps to create documents, share information, collaborate on projects and work together regardless of location.

Most popular tool available are:

1. Angular JS
2. ASP.NET
3. Ruby on Rails (ROR)
4. Symphony
5. Laravel

Two components of web application:

• It is an application for accessing websites.
• First web browser, called WorldWideWeb, was created in 1990 by Sir Tim Berners-Lee.
• Used to retrieve data from webpages.
• Multiple web browsers can be installed on a single device.
• Allow us to access information using the WWW.
• Without a browser, you can’t open a single website.
• Retrieves information from other parts of the web and display it on your desktop or mobile devices.
• Example: Chrome, Firefox, Mozilla, Opera, Internet Explorer.

• A web server delivers static web content e.g. HTML page, files, images, video etc.
• An application server generates dynamic content such as transaction result, decision support on real time analytics.
• Web server arrange the run environment for web application.
• Application server arrange run environment for enterprise application.
• Web server is less fault tolerant.
• Application server is high fault tolerant.
• Web server example are Apache HTTP, IIS.
• Application server example are JBoss, Glassfish.

• Content of any website for a business organization, companies text, images, media etc are stored in database like MySQL.
• We need to connect to database, querying it for data and presenting data in HTML is done by a server side scripting languages such as PHP.

1. Prepare database user account details.
2. Use one or more server side scripts to connect to database.
3. Query your data using SQL (Structured Query Language).
4. Output your data. Now we can present it within HTML.
5. Test your script. Once we have established successful connection, we can build website.

<?
mysql.connect("database.host",
              "username",
              "password");
?>

SELECT * FROM Customers;

The web app development life cycle typically involves following 7 stages.