ASP stands for Active Server Pages. ASP.NET is an open-source, server-side web application framework developed and marketed by Microsoft for web development to produce dynamic web pages. It allows you to use a full featured programming language such as C# or VB.NET to build web applications easily. It provides great integration of HTML, CSS and JavaScript. It is built on the Common Language Runtime (CLR) and allows programmers to write code using any supported .NET language.