ASP.NET is a popular open-source web framework developed by Microsoft, designed to facilitate the creation of dynamic web applications and services. Launched in 2002, ASP.NET is part of the .NET platform and enables developers to build robust and scalable web applications using a variety of programming languages, most notably C# and VB.NET. This framework offers a powerful set of tools, libraries, and an extensive ecosystem, making it a preferred choice for both small-scale projects and enterprise-level applications.