Basically an administrator takes advantage of Adobe AEM user manager tool to grant privileges and using this tool he can arrange well all main security policies needed, but there are some scenario that requires an advanced configuration and must be done in a different way.
For example, if you need to grant permission to view and edit pages only under  a specific subpage tree of the repository, apparently it could be an easy task to do but it would eventually reveals hard to arrange.

Let’s try to schematically represent a repository structure to analyze:

Our goal is to provide a full access to SubHome2 page and all its children, not allowing to see other pages (i.e. SubHome1, it language, etc..).
It would have been easy to grant a jcr:all privilege to SubHome2 but Adobe AEM tools are based on path browsing, consequently all folders composing the requested path must be visible to get access.
In the bullet list above  in fact, we can distinguish:

• Green: Pages with full access
• Orange: Pages with a partial read access (basically only the cq:Page and cq:PageContent nodes)
• Gray: Pages not visible

To apply a security configuration like this we have to use CRX tool (under Access Control tab) and configure for each folder the policies listed below, leveraging the restriction management provided by Jackrabbit OAK (Documentation).

View table on plain text format
Hint: To set an empty rep:glob value fill the input field with two double quotes (“”)

Once done final user will be able to use all standard AEM tools and properly manage his area, preserving resources outside of his focus range