A web application is any application that uses a web browser as a client. The application can be as simple as a message board or a guest sign-in book on a website, or as complex as a word processor or a spreadsheet.

What is a Client?

The 'client' is used in client-server environment to refer to the program the person uses to run the application. A client-server environment is one in which multiple computers share information such as entering information into a database. The 'client' is the application used to enter the information, and the 'server' is the application used to store the information.

What are the Benefits of a Web Application?

A web application relieves the developer of the responsibility of building a client for a specific type of computer or a specific operating system. Since the client runs in a web browser, the user could be using an IBM-compatible or a Mac. They can be running Windows XP or Windows Vista. They can even be using Internet Explorer or Firefox, though some applications require a specific web browser.

Web applications commonly use a combination of server-side script (ASP, PHP, etc) and client-side script (HTML, Javascript, etc.) to develop the application. The client-side script deals with the presentation of the information while the server-side script deals with all the hard stuff like storing and retrieving the information.

How Long Have Web Applications Been Around?

Web Applications have been around since before the web gained mainstream popularity. For example, Larry Wall developed Perl, a popular server-side scripting language, in 1987. That was seven years before the Internet really started gaining popularity outside of academic and technology circles.

The first mainstream web applications were relatively simple, but the late 90's saw a push toward more complex web applications. Nowadays, millions of Americans use a web application to file their income taxes on the web.

What is the Future of Web Applications?

Most web applications are based on the client-server architecture where the client enters information while the server stores and retrieves information. Internet mail is an example of this, with companies like Yahoo and MSN offering web-based email clients.

The new push for web applications is crossing the line into those applications that do not normally need a server to store the information. Your word processor, for example, stores documents on your computer, and doesn't need a server.

Web applications can provide the same functionality and gain the benefit of working across multiple platforms. For example, a web application can act as a word processor, storing information and allowing you to 'download' the document onto your personal hard drive.

If you have seen the new Gmail or Yahoo mail clients, you have seen how sophisticated web applications have become in the past few years. Much of that sophistication is because of AJAX, which is a programming model for creating more responsive web applications.