A Web application is any computer program that performs a specific function using a Web browser as a client. The application can be a simple contact form on a website or as complex as a word processor.
Most Web applications rely on the client-server architecture in which the client enters information while the server stores and retrieves information. Internet mail is an example.
In recent years, there has been a huge push for the development of web applications for functions that normally do not require a server to store information.
Web applications can provide the same functionality and gain the advantage of working across multiple platforms. For example, it can act as a word processor, store information in the cloud, and allow you to “download” the document to your personal hard drive.