ASP.NET is a Microsoft server-side scripting technology that evolved from the earlier Active Server Pages (ASP), also referred to as classic ASP. It enables the execution of scripts embedded in web pages through the IIS server and offers enhanced features such as better language support, event-driven programming, and user authentication. ASP.NET is part of the .NET framework, designed to improve web application development by providing a rich set of tools and controls, while not being fully backward compatible with classic ASP.