if this page for authorized members you refer to is not for regular visitors, then yes, it would be a protected page.
If it wasn't protected, then, potentially, anyone could view it.
Using a tool such as security assist, the page is coded to check that the visitor has logged in and that the login has appropriate rights to view the page.
If the check is ok, the page is displayed, if not, the visitor is pointed somewhere else, such as a login page.