How do user security permissions apply in sharepoint 2013?

Hi all.

I'm just wondering how this works in a nutshell.  I've googled about it and read that by default sharepoint 2013 uses claims based authentication, and that this is likely the type of authentication we would be advised to use.  So assuming we would use claims based authentication, does this incorporate AD permissions also for already existing network shares, folders and files which may be shared or sent around by a user who maybe should not be sharing this information with others that do not already have permissions to it?

I assume that claims based authentication is understood and compatible with IIS website permission security also, is that true?