This plugin manage user permissions across the site
THe Auth logic will follow these principles:

Users belongs to AuthRole
AuthRole hasAndBelongsToMany Permissions

So one user could have 1 role in the system, either it be Admin, or News editor or other type of content
This user is inserted into special table which distinct that the user has special permissions from the rest of normal users
Each role has set of Permissions and the system will check if the user has right to view the specified url

Tables:

auth_users - hold user reference and role reference (it could be described as HABTM between User and Roles)
auth_roles - hold roles definition
auth_permissions - hold permissions stored as preg_match pattern of the url
auth_roles_permissions - hold HABTM relation between Roles and Permissions