Object Hierarchy graphically displays two level child hierarchies for a particular record. For example if used within an account record, it will display all child contacts, accounts, opportunities and custom object of this account, and also the children of these child contacts, accounts, opportunities and custom object.
User can expand and collapse the hierarchy tree by clicking on the icon appearing before the record name on any level.
After configuration, a button can be added to any object. Clicking on this button brings up the Object Hierarchy in a new tab.
The tool is available as a free app on AppExchange.
You can also refer the User Manual for further details, from here.