There are two types of User records held on the website:

1. Joomla users: these are responsible for  controlling access to the website, and hold details of a members email address and their full name. It is possible to also have a third identifier as "User name", but this is potentially so confusing is is strongly discouraged. The recommended approach is always to use the email as User name, sincle this will always be unique and easily remembered.
2. MailMan users: if the optional MailMan component gas been installed, there will also be a separate list of records to hold details of the member's preferred name and group affiliation. A MailMan user cannot be created unless a coresponding Joomla User record exists.

Users are maintained from their own entry on the main Joomla menu, and the standard mechanism for Add and Update are available. It is mandatory to specify their name in full and their email address, abd as mentioned abofe, although it is possible to give a third identify or nickname to be used when logging in, it is much better to avoid confusion and just enter the email address twice, once for “Login Name” and again for “Email”.