Web applications have interactive functionality as their focus. Websites have the consumption of what a human, and not an HTML parser, would call a "document":

Web applications have interactive functionality as their focus. Websites have the consumption of what a human, and not an HTML parser, would call a "document": video, text, and images. They may not be statically served, but their code exists to facilitate the serving of what are recognizably documents. Wordpress's backend is a web application. That web application exists to drive the website that is its frontend. Not really a controversial standpoint, I don't think, except amongst the hyper-literal who but-for about comment features (hence the use of "focus" above).