With Access Control Levels (ACL) setup on your site, you can have different levels of what can be viewed by those visiting your site.
Levels can include general public, site registered general public, campaign staff, and site administrators.
Using ACL you control who can see the various element features and articles posted on your site.
Any item that is set to 'Public' is viewable by anyone visiting your site.
'Registered' users can view anything in the public settings and whatever else you assign to this access level. No changes to the article postings or other feature elements are usually allowed here. It is recommended that if you have the feature element which allows for site visitors to post comments on any articles you assign that feature in this ACL group.
Campaign staff can view all lower levels items. They can also be allowed to edit posted articles and submit new articles for posting though they are not usually allowed to do the same for other feature elements.
Site Administrators are at the top of the of ACL hierarchy and can do most anything prohibited to the lower ACL groups. This includes reviewing and authorizing submissions for posting.
The Login Form feature element at right is how one gains access to the stuff in the higher levels. You can allow for general site visitors to self-register for the site or not. Normally, a self-registered visitor will be placed into the 'Registered' ACL group. The self-registration feature is not enabled on this site.
As part of the self-registration process an email is sent to their submitted email address to verify a legitimate registration. There will be a link in that email they have to click and visit to activate their registration. Their login username and password will not be usable until they complete this process.
Placing someone in a higher ACL is a task normally reserved for someone already in the Site Administrator ACL group. If the person is already self-registered (if this is enabled) you simply update their assigned User Group from within the Site Administration pages. If not already registered, a Site Administrator can manually add the new user, place them into the appropriate ACL group and activate their registration. A Site Administrator can also revoke or suspend any registered user.