This new tool, called "Rights details", lets you understand why a user has a particular right.
It is available in the Users, groups and rights tab, as well as in the Content tab.
The tool inspects the rights of the current selection, or of the general context if there is no current selection.
To access the tool, there are two different rights: "Explain your rights" to view an explanation of your own rights, and "Explain a user's rights" to view an explanation of any user's rights.
For more details on this feature, please visit this page.