look here https://en.wikipedia.org/wiki/ASP.NET
ASP.NET is an open-source server-side web application framework designed for web development to produce dynamic web pages. It was developed by Microsoft to allow programmers to build dynamic web sites, web applications and web services.
These are some things that ASP.NET adds to the .NET platform:
Base framework for processing web requests
Web-page templating syntax, known as Razor, for building dynamic web pages using C#
Libraries for common web patterns, such as Model View Controller (MVC)
Authentication system that includes libraries, a database, and template pages for handling logins, including multi-factor authentication and external authentication with Google, Twitter, and more.
Editor extensions to provide syntax highlighting, code completion, and other functionality specifically for developing web pages