Lessee, C++ introduces classes (which include the ability to overload operators), uses streams for most IO functions (cout, fout, etc), adds the bool type, templates, and I think that's about it (though those changes alone are quite significant).
The string type isn't technically a built-in type. It's part of the standard C++ library. The new features that C++ offers (namely, classes and operator overloading) are what allows them to appear to be integrated into the language.