In a UML diagram, what does an asterisk (*) indicate?

UML diagram:

Commission +COMMISSION_RATE: double = 0.10 +addSales(sales: double): void Commissioned -sales: double = 0.0 +Commissioned(name: String) +addSales(sales: double): void +getPay(): double Salaried And Commissioned -sales: double +SalariedAndCommissioned( name: String, salary: double) +addSales(sales: double): void +getPay(): double Salaried2 -salary: double Employee2 -name: String +Employee2(name : String) +get Pay(): double +printPay (date: int) : void +Salaried2(name : String. salary: double) +getPay(): double Hourly2 -hourly Rate: double -hours: double = 0.0 +Hourly 2(name : String. rate: double) +getPay(): double +addHours Payrol13 (hours: double): void +main(args: String[]): void