At the point when you create a Web Page you have the option to create a blank Web Page or to create a sample application using one of the Web Page Templates.
If you create a simple Web Page, you will need to design the entire interface including themes, layouts, responsive design or any other features you want to incorporate.
If you start by using a Web Page Template this will give you a framework for building your application as it creates a Home Page and all the supporting Reusable Parts, as well as a Theme and a Server Module. Even if the Web Page Template is not exactly what you want or need it can provide a useful structure as a starting point for your application.