C# is an object-oriented programming language developed by Microsoft that is similar to C++ but simplified. It can be used to create a variety of applications including Windows forms, web applications, web services, and .NET components. Some key features of C# include being type-safe, object-oriented, and compatible with other .NET languages. It also provides modern features like automatic memory management and support for error handling. C# aims to combine the best aspects of languages like C++, Java, and Visual Basic.