The DotNet SDK (Software Development Kit) is a set of tools and libraries designed to help developers create applications using the DotNet platform. It includes compilers, runtime libraries, and command-line tools that simplify the development process for various types of applications, such as web, mobile, and desktop software. With the DotNet SDK, developers can build applications in multiple programming languages, including C#, F#, and Visual Basic. The SDK also provides templates and sample projects, making it easier for beginners to get started and for experienced developers to streamline their workflow.