Explanation
Setting the Organization-Wide Defaults (OWD) for the Case object to private is a configuration that can help to protect sensitive HR data in Employee Experience Management. Employee Experience Management is a prebuilt app that comes with Public Sector Solutions. It can help public sector agencies to manage employee programs and benefits, such as leave requests or wellness surveys. The Case object is a standard object that can be used to track employee requests or issues in Employee Experience Management. Setting the OWD for the Case object to private means that only the owner of the case and users above them in the role hierarchy can access the case record by default. This can prevent unauthorized access to sensitive HR data by other users.
Reference:https://help.salesforce.com/s/articleView?id=psc_admin_setup_employee_experience.htm&type=5&l