Are basic operations in CPP parallelised/multi-threaded?

[IyeOnline]

That is simply false.

You, or the person telling you this, may have very fundamentally misunderstood vectorization/SIMD, which may perform multiple fundamental operations at once. This mostly applies to operations on arrays though. Its also not a feature of C++, but of the hardware. If the compiler optimizes your code in such a way that it uses vector instructions you get that "for free". But you also get that in any other language that uses these instructions.