Users Tab Shows a list of all users and can be modified by clicking on their name and viewing their information as well as applying user roles to that user by clicking the ACL Rules link to the right. You can set User options by clicking the User Options link as as well as Delete a user by clicking the Delete link.

Groups Tab Allows you to create user groups and appy ACL Rules by clicking the ACL Rules link to the right. Fill out the details than click Save. You can also add particular users to a particular group as well as removing groups.

Properties Tab Control weather users can register on your site, set which group new users will be assigned to, authentication methods etc.