PAM and login.conf the login process

[Sean Murphy]

I am trying to understand how users login and what does the system do 
specifically with validating the passwords and change passwords.

when I login at the console is the login/password information passed to 
PAM and does PAM check the login.conf for certain characteristics and 
then check the password file? Or does the login.conf only apply after 
the user has logged in?

Does the login.conf effect only shell accounts or can PAM check the 
login.conf to see if a user meets the minimum password change requirements?

For example I am using poppassd for users to change there passwords. 
The minimum is set in the login.conf for 6 characters.  If the user 
types less then 6 for his password will it error or reject the request? 
  Or does the login.conf only apply when in shell and not through daemons.

Thanks