The .NET Framework is a software development platform created by Microsoft for building and running applications on Windows. It provides a large class library, known as the Framework Class Library (FCL), and supports multiple programming languages, including C#, VB.NET, and F#. The framework includes tools for building desktop, web, and enterprise applications, and it provides features such as memory management, security, and exception handling. The .NET Framework is known for its robust runtime environment, the Common Language Runtime (CLR), which manages the execution of code, making it easier for developers to create cross-language applications.