The Pluggable Authentication Modules (PAM) architecture on UNIX systems, provides an extendable design to enable customized behavior with respect to user authentication. The PAM Password Synchronizer Plug-in leverages the UNIX PAM architecture to enable password change notifications to be propagated to the TDI Plug-in Password Store.
There are numerous online documentation sites describing all aspects of PAM. The AIX online manual has a good overview description at the following link:
http://publib16.boulder.ibm.com/pseries/en_US/aixbman/security/pam_overview.html#plugauthmod.
The primary purpose of the PAM Password Synchronizer Plug-in is to intercept password change events that originate from UNIX based tools and PAM enabled applications, like the "passwd" command.