You may want to provide information for specific audiences.
If you create documents collaboratively, you may want to show some of the information in a page only to other team members that for instance, have write permissions for that page. This is not sensitive information, but may include sections that need rework or show just an outline of what will get into. Or you may want to show which documents transclude from this page. This information may be very relevant for authors, but is typically irrelevant for all other audiences.
If you need to show some content on a page only for a specific audience, the hide macros may be very convenient: Hide From Anonymous User Macro or Hide From Reader Macro.
In addition to that the Section Macro and Content Marker Macro provides parameters that help to hide the page fragment.
Note the word 'hide'
The fragment is still on the page and can be accessed by anyone. This is because the page can be fetched in its storage format easily.
So do not hide sensitive information on a page. The hide feature is simply a convenience for the reader.
If you actually need to secure information, you probably need to install a third-party add-on.
