Business Unit
Business units are used as cost reporting entities for timekeeping expenses.
Employees are associated with a specific business unit so that when they report time charges, the costs are charged against that business unit. Your implementation will use the business unit to indicate whether to cost timesheets by employee wage rate or craft rate.
The system uses double entry accounting. For example, when time is booked against an activity, the system debits the cost centers on the activity and credits an offset account. In this case the offset account would be the payroll cost center defined on the crew member or employee's business unit.