Users are everyone who have created an account at CPDL. Regular users can edit almost every page in CPDL, such as the composer and works pages, and can create new pages as well (but cannot delete them).
Autoconfirmed users are all users who have introduced a valid email address and confirmed it, by clicking on a special link received by email. Autoconfirmed users can do everything regular users do. After they have reached a minimum number of edits, they are also allowed to move (rename) pages to other titles.
An automatically updated list of registered users is available here.