Web application build using Razor Pages. Razor Pages is a simplified and easier-to-use page-based web application programming model that focuses on using a file-based routing approach eliminating much of the workload that ASP.NET MVC introduced.
ASP.NET Core is the web side of .NET Core development. Under this umbrella are three major components - Razor Pages, MVC, Blazor, and API. All of these project types can co-exist in the same website without an issue, yet they all fill a different role.
.NET Framework Architecture is a programming model for the .NET platform that provides an execution environment and integration with various programming languages for simple development and deployment of various Windows and desktop applications. It consists of class libraries and reusable components.
.NET Framework Architecture Diagram