Whether you need a website or web application depends on what features you want to offer. A typical website is informative, and can consist of either multiple pages or a single page with multiple areas (like the one you're looking at right now for instance!). A specific layout usually structures the website's content. There is little to no user input present on a website, hence a website can be hosted without the need of a 3-tier-architecture (UI, Services, Database), and instead a simple webspace is enough to publish the website. Websites are generally faster developed, and therefore cheaper than web applications.

A web application on the other hand is a website with user input. Login, forms, controls, etc. allow the user to interact with the website and its content, and the web application is able to store and retrieve data from a database. The development requires the setup of a 3-tier-architecture (UI, Services, Database), and therefore is more complex. A web application can be deployed to a private server, or to a cloud server such as Microsoft Azure or AWS.