Thanks for the correction, Microsoft calls it the C Runtime/CRT. It‘s unfortunately complicated, and I’ll completely ignore static linking, which is possible, but not supported in many scenarios involving DLLs.
It used to be the case that the CRT shipped with Windows (msvcrt.dll). That file is now considered legacy/deprecated and is no longer supported by current compilers. For several years after that, you always had to redistribute the CRT (msvcrtXXX.dll), even for pure C support.
The current state of affairs is that the CRT is split into several files, some of which come with Windows update (the so-called UCRT) and some of which are compiler-specific and have to be redistributed. C++ std support requires yet more files.
This document gives an overview: https://docs.microsoft.com/en-us/cpp/c-runtime-library/crt-l...
