Asp.net is web application framework developed by Microsoft to build dynamic data-driven Web Application and WebServices.
Asp.net is basically a subset of wider .NET framework. A framework is nothing but a collection of classes.
In .NET Framework you can build Console application. Web Application, Window Application, Mobile Application. So for web application ASP.net is being used.
ASP.NET is the successor to classic ASP (Active Server Page.)
What is Web Application?
A web application is an application that is accessed by users using a web browser such as: