Is 'marc' some person in the Linux/Unix community?
/etc/aliases on a default centos install, the bottom line reads:
# Person who should get root's email # root: marc
Or is it just a random name?
This is an example, but it wasn’t picked out of thin air:
marc is Marc Ewing, who created Red Hat Linux and wrote the initial version of the
/etc/aliases file which ends up in CentOS.
The line is commented out, so it doesn’t have any effect; if you want to redirect email sent to root, it’s up to you to choose whatever recipient is appropriate, correct the line to take that into account, and uncomment it.
Correction to the first part of my answer even though another answer has been accepted:
It's not entirely random but Marc Ewing, the creator or Red Hat and writer of the initial
/etc/aliases (just providing to give clarity).
If you'll notice, the line is commented out.. If you wanted to set an alias for mail going to
root then you'd uncomment the line and replace
marc with other users or email addresses that you want to get mail addressed to