ASP.NET is not a single language, but it is a set of development tools from Microsoft for web development. It is easy to do development using ASP.NET than traditional methods because of the visual interface provided in Visual Studio .NET and Visual Web Developer. Developers can write their own code and scripts and embed into ASP.NET website also. Although ASP.NET appears like a successor to classic ASP, but actually its scope is wide and it also supports Visual Basic .NET, JScript .NET and some open source languages like Pert and Python etc.
ASP.NET is built on .NET framework. In order for a web server to run ASP.NET websites it must support .NET framework. Microsoft's Internet Information Server (IIS) is most widely used for ASP.NET websites.