ASP.NET is a web application platform that runs on the .NET framework. It allows building web applications using languages like VB.NET and C#.NET. ASP.NET contains HTML, server controls, style sheets and client scripts. Visual Studio 2008 is an IDE that helps design, develop and deploy ASP.NET applications. The document provides tutorials on creating ASP.NET web projects, using server controls, handling events, working with databases and grids, and managing state with sessions and cookies.