Microsoft .NET is a software development framework created by Microsoft that allows developers to build and run applications on various platforms. It provides a large library of pre-coded solutions, known as the Base Class Library, which simplifies the coding process and enhances productivity. The framework supports multiple programming languages, including C# and VB.NET, enabling developers to choose the language that best fits their needs. With its ability to create web, desktop, and mobile applications, Microsoft .NET is widely used in the software industry for developing robust and scalable solutions.