The benefits tab keeps track of the plans that employees are enrolled in. This tab can be very useful in a number of ways. You can have the payroll system set up to feed the Benefits listed here to control the deductions that employees have taken out of their checks. You can use this data to determine Cobra Eligibility, other common uses of this data is for preparing Employee Benefit/Cost Summaries and during open enrollments.
The Payroll Sync and Preview Payroll Sync allow you to update the deduction and/or earning associated with this Benefit and to be able to preview what effect the update will have. This buttons have the same effect as the buttons on the Payroll Sync tab but here they only affect the currently selected benefit.