i test code i post with my hardware but try to leave the existing HW parameters.
line beginning with # are compiler directives. #ifdef/#else/#endif effectively comment out code. when i tested, MyHW was defined ("#define MyHW) and the PINs after #ifdef MyHW took effect. MyHW is undefined and your PINS values will take effect
another common usage is
#if 0
...
#else
...
#endif
to effectively remove/comment out code when trying different things