Is CUSTOM ROM is a modified Kernel of Android OS or Firmware (BIOS) ?

Question

Question on @Quora: Is custom ROM a remodeled kernel of OS (Android), firmware (BIOS), or any other thing?
Any body knows the answer, please try to clear my doubt via the sololearn platform or in this quora link itself
------------I always welcome yours Response---------
https://www.quora.com/unanswered/Is-custom-ROM-a-remodeled-kernel-of-OS-Android-firmware-BIOS-or-any-other-thing?ch=18&oid=112945066&share=4533b89b&srid=ht8cB9&target_type=question

Answer 1

A CUSTOM ROM is a modified kernel.
CUSTOM ROM is basically made by modifying the operating system you already have in your Android device.

Answer 2

Thank you Raju 😄 for yours valuable comment