"Employment Details" tab lists all the information about that specific person's current, or past employment with your company.
To get to an employees "Employment Details" go to "Manage > HR > Employees" and select the employee you wish to view.
Once you have selected an employee, you will be prompted with their "Identity" page. If you look two tabs to the right you will see "Employee Details", select this, you will see various fields where you can change details regarding their employment.
Information such as whether they are currently employed, to what branch they work for, and more can all be altered from this tab.
Press "save" after changing any information, or "cancel" to not record any changes made.