Windows Forms is a robust programming environment for building Win32 client applications. It provides great support for Win32 developers, improved ease-of-use and reliability, and easier deployment. Windows Forms allows you to create Windows-based applications using the .NET Framework. This framework provides a clear, object-oriented, extensible set of classes that enable you to develop rich Windows applications. Additionally, Windows Forms can also act as the local user interface in a multitier distributed solution.
See the following topics in the .NET Framework SDK documentation: Introduction to Windows Forms