Windows Runtime Projections are the way that the Windows Runtime APIs are exposed in each language. This may be at compile time (as in C++) or at runtime (as in JavaScript) or a combination (as in C#). Each language decides how to present the WinRT APIs best. Most of the time it is a direct exposure, but other times there are wrappers or redirections that may take place. Delegates and events are a good example. In C# they show up as C# delegates/events and not as WinRT-specific types. Strings likewise are remapped to be the native language string type and not the underlying hstring type.