What is the difference between Website and Web Application? A website is defined by its content, while a web application is defined by its interaction with the user. That is, a website can consist of a static content repository that's dealt out to all visitors, while a web application depends on interaction and requires programmatic user input and data processing.
For example, a news site would be a "website", but a spreadsheet or a collaborative calendar would be web "applications". The news site shows essentially the same information to all visitors, while the calendar processes individual data.
Practically, most websites with quickly changing content will also rely on a sophisticated programmatic (and/or database) backend, but at least in principle they're only defined by their output. The web application on the other hand is essentially a program that runs remotely, and it depends fundamentally on a processing and a data storage backend.
A website is visited once or twice by a single user. A web application, can be visited dozens of times per day, meaning we need to focus on designing for efficiency!
While working at Alfresco, I was using our local team share Application. This is an alternative to Dropbox but with a more powerful features. For this project I took a landing page and converted it from the website to Web application.
On the landing page you can see different types of widgets: my activities, my documents, my tasks, my sites. All the widgets are constantly updating. It is clear that team members use this website in their work very often. Regarding the what was said above I tried to update it with the simple design enhancements.
The idea was to take the original skeleton and create a simplified version with modern web application design. And here is the result.
Websites are primarily informational. In this sense, http://cnn.com and http://php.net are websites, not web applications. Web applications primarily allow the user to perform actions. Google Analytics, gmail, and jslint are web applications. They are not entirely exclusive.
A university website likely gives information such as location, tuition rates, programs available, etc; it will likely have web applications that allow teachers to manage grades and course materials, applications for students to register for and withdraw from courses, etc.
Business software is only used because it helps people complete tasks. They have a job to do and they want to get in and get out. It is critical that you design for these different flows to make your user's job as easy as possible.