The primary reason for setting up web users and groups is to be able to secure access to selected pages on the web. Users on the web are stored separately and apart from admin (back-end) users for security reasons. A web user cannot log into the back-end nor can a back-end user log into the web site (front-end). You would have to use separate accounts to do this. Here's how it works:
Back-end users are assigned to back-end user groups:
Web users are assigned to web groups:
Both "Back-end User Groups" and "Web User Groups" can be assigned to the same "Document Group".
From the Web (Front-end):
From the Admin (Back-end):