.NET is a versatile, open-source platform designed by Microsoft for diverse application development. Its backbone is the Common Language Runtime (CLR), managing code execution and providing crucial system services. It enables developers to write .NET apps in languages like C#, F#, and Visual Basic. .NET’s Framework Class Library (FCL) provides pre-coded solutions, streamlining common tasks and enhancing code reliability. Key features include Language Integrated Query (LINQ) and cross-platform support.