difference between passWORD, passPHRASE; allowed devices won't connect; routerlogin.net not secure?

> i am in the process of trying to really learn how this stuff works,
> [...]

   Visit http://netgear.com/support , put in your model number, and look
for Documentation.  Get the User Manual, and do some reading.  You might
start with the section, "Types of Logins".

> [...] tell me what the difference is between a passWORD and a
> passPHRASE in reference to the c3000 modem/router?

   Generally, a password is a single group of characters without any
spaces; a passphrase is similar, but can include spaces separating
multiple words.  (See that "Types of Logins" section in the User
Manual.)

> my second question is regarding the "allowed device list"   i have
> entered all of my device information and it has successfully saved, but
> when i try to access wi-fi, it doesn't work.  it says authentication
> difficulties (something like that).

   "it doesn't work" is not a useful problem description.  It does not
say what you did.  It does not say what happened when you did it.  As
usual, showing actual actions with their actual results (error messages,
...) can be more helpful than vague descriptions or interpretations.
"(something like that)" is much less useful than an actual quotation of
an actual message, too.  Does the wireless network stuff work if you
disable the access control feature(s)?

> [...] when i am on the routerlogin.net page it shows that it is NOT a
> secure website and my information is "vulnerable" ...  how can that
> possibly be right?

   That's easy.  You're accessing the router's web server using
"http://" (which works), not "https://" (which, I'd guess, does not
work).  Many modern web browsers complain about an
(unencrypted/insecure) "http://" connection when you need to send data
to the server (like your user name and password).  In this case, you're
talking to your own router, not some computer in the outside world, so,
although the connection is not encrypted/secure, the risk is slight.