understanding bootloader unlocking I am trying to understand the rooting procedure in general.
I see that 1st stage involves what it termed as
"unlock bootloader".

It is described as a method which makes the bootloader capable for using non-manufacture images.
If I understand correctly the bootloader, shall not boot non-manufacture kernel/ROM unless it is unlocked.

Yet, many rooting are done by just programming the recovery image.
But the bootloader is not the recovery image.

So, how can it be that root is gained with just the recover if 1st stage is unlocking bootrom ?

Thanks,
ranran
Unlocking the Bootloader is required in some process including unofficial ROM, Kernel,Recovery, etc to avoid Hardbrick or Softbrick caused by non-manufacturer file or data (not integrated with bootloader default information)

It is required if you want to Root your phone by unlocking the OEM in the Developer Settings