Can I get an overview of makesdna and makesrna?

What is makedna’ s and makesrna’s purpose**?** How do they relate to and contribute to the rest of blender code**?**

Where does the code found in files like:
build_windows_Full_x64_vc15_Release\source\blender\makesrna\intern\RNA_blender_cpp.h

originate from**?**

Thanks

See here:
https://en.blender.org/index.php/Dev:2.5/Source/Architecture/RNA
https://en.blender.org/index.php/Dev:Source/Architecture/SDNA_Notes

Thanks. I’ll check it out.