C++20 is a major update to the C++ programming language, introducing new features and improvements that enhance its usability and performance. Key additions include concepts, which allow developers to specify template requirements more clearly, and ranges, which simplify working with sequences of data. Other notable features are coroutines for asynchronous programming and the spaceship operator for easier comparison of objects. This version also includes enhancements to the standard library, such as new algorithms and calendar/time zone support. Overall, C++20 aims to make the language more powerful and easier to use, catering to modern programming needs and practices.