Interesting................
The Path is needed for the bin...binary...files most C++ compilers rely on. Persumably the standard C libraries are also stored in there...have a look for stdio.h if you want to verify this...most C++ installs include the standard C libraries. Not sure about the other thing though. Does this contain the actually IDE and compiler and linker?
The path is needed to allow the C++ process to find the required compiler/help/linker etc program binary files which you will need in order to write and compile your apps.
Just checked this PC, (Borland C++ compiler) it also adds a lib subfolder to the path.