voluntary, intentional, deliberate, willing mean done or brought about of one's own will. voluntary implies freedom and spontaneity of choice or action without external compulsion. a voluntary confession; intentional stresses an awareness of an end to be achieved. the intentional concealment of vital information deliberate implies full consciousness of the nature of one's act and its consequences. deliberate acts of sabotage
PAM is a framework that assists applications in performing what I'll call authentication-related activities. The core pieces of PAM are a library (libpam) and a collection of PAM modules, which are dynamically linked libraries (.so) files in the folder /lib/security.
Authentication is a process of proving that someone is who they say they are. In Web applications, authentication generally consists of two parts: querying for credentials (usually by some interface that requests a login name and password) and verifying those credentials against some source (such as a database).