Users can register themselves when they click on "New User" in the "Login" page.
They fill out some contact information, including the Email and then get a password sent to them by Email. This is to verify that the Email is valid.
New users have the right to add talks to the Discussion pages or other rights if configured by the System administrator.
If the user has lost the password, a new one can be created. The old cannot be recovered, it is not saved in the wiki, only a MD5-footprint of it.