@Martin
The view you have provided is true but abstract or general. Its just like saying an OS is an OS, a program is a program .......true but there are subtypes/subcategories.
Website is the general term...not a web app, that refers to A collection of HTML and subordinate documents on the World Wide Web that are typically accessible from the same URL
But has more recently come to be accepted as a WEBSITE that doesn't accomplish anything other than displaying information.
A WEB APP on the other hand is An application that is accessed via a web browser over a network such as the Internet or an intranet designed to help the user to perform a singular or multiple related specific tasks e.g. Instant Messaging, word processing, playng GAMES, Managing Accounts and Inventory.... just like a desktop app would.