How does the kernel boot start?

Question

linux

If you start with grub, then it initializes the kernel image which is /boot/vmlinuz...
Next, this file starts the init process.
I can't figure out where this init comes from. There is /sbin && /etc/init && init.d/
What is responsible for what?
Correct where wrong

Answer 1

/sbin/init, what could be incomprehensible here? /etc never had executables, only settings. But the launch of init (or by the way systemd) is not at all the beginning of the kernel boot, but rather its completion;)