before login:
after login:
these files show info on shell login, on ssh login, but i don't remember if FTP will use them too...
i don't use RHEL, so i don't know the caveats of it, on Debian they are generated using templates on each boot, so you are not supposed to touch them, instead you need to edit the templates.
i will not give you more info, because you are a student and you must learn how to look at the documentation yourself.
remember, in a enterprise distribution like RHEL or Suse, the available manuals are your best friends.
in other time, the answer at your question would be as simple as "RTFM" (Read The ..... Manual)
best regards