Manual accounts
The manual accounts authentication plug-in removes any way for potential users to create an account for themselves on your moodle site.
The only available account creation options are either for an admin to manually create an account by filling in a new user form, or for user accounts to be created from a flat-file upload.
The configuration screen for manual accounts provides a box for creating the user instructions (normally along the lines of "A valid ID and Password are required to access this system. Please contact the VLE office for help with this").
It also provides the option to lock certain fields in the user account record to prevent users from changing them, the ability to enable or disable guest access, and finally, the configuration page provides a way for admins to use an alternative login screen.
These latter options are also available in the other authentication plug-in configuration pages.
(More detail to come)