[gentoo-user] mount -o bind /dev /mnt/gentoo/dev

[Ran Shalit]

Hello,

I am a beginner with Gentoo.
I have followed the instruction for the installation, and tried to see
that I really  understand all of them.
There is the command:
mount -o bind /dev /mnt/gentoo/dev
Which I'm not sure I really understand.
1. What is the difference between doing thses mount to just copy the
contents of /dev into /mnt/gentoo/dev?
2. Another thing I've noticed is that some tutorial add to the above
also bind to sys folder , and other do not include it.
mount -o bind /sys /mnt/gentoo/sys
Therefore I would like to ask if it is really required ?

Thank you,
Ran