PAM modules that are referenced in the configuration files can be located with this command:

ls /lib/*/security

returns:

pam_access.so      pam_gnome_keyring.so  pam_nologin.so     pam_tally.so
pam_cap.so         pam_group.so          pam_permit.so      pam_time.so
pam_cifscreds.so   pam_issue.so          pam_pwhistory.so   pam_timestamp.so
pam_debug.so       pam_keyinit.so        pam_rhosts.so      pam_tty_audit.so
pam_deny.so        pam_lastlog.so        pam_rootok.so      pam_umask.so
pam_echo.so        pam_limits.so         pam_securetty.so   pam_unix.so
pam_env.so         pam_listfile.so       pam_selinux.so     pam_userdb.so
pam_exec.so        pam_localuser.so      pam_sepermit.so    pam_warn.so
pam_extrausers.so  pam_loginuid.so       pam_shells.so      pam_wheel.so
pam_faildelay.so   pam_mail.so           pam_stress.so      pam_xauth.so
pam_filter.so      pam_mkhomedir.so      pam_succeed_if.so
pam_ftp.so         pam_motd.so           pam_systemd.so
pam_gdm.so         pam_namespace.so      pam_tally2.so
. . .

Look in this directory to see what kind of modules are available to use.

Almost all of the modules have man pages, which can describe their usage. For example:

man pam_access