An ASP.NET page can be thought of as just like an HTML page that have certain sections marked up for special considerations. An ASP.NET file is created by saving it with the file extension ASPX. Web servers are configured to looks for files with this extension and process by the ASP.NET module (aspnet_isapi.dll) in the Web Server.
Unlike ASP pages which used to be written in VBScripts and/or JavaScripts, an ASP.NET page is written with a full-blown programming language. Several programming languages are supported to develop an ASP.NET page, and VB.NET is the default language.
There are three ways of placing ASP.NET codes in a Web page: