why where how runbasebatch class is used?

 have to develop using  RunbaseBatch class, which will calculate the Interest on Provident Fund balance.

·         Considering “Customers” as employees.

·         Get the Customer balance by summing up the Amount Currency field which is my opening balance for PF balance.

·         Interest will be taken from the Parameter table .

·         Calculation must be saved in history against every employee.

·         Calculation of interest will go month wise in order (February interest cannot be calculated before January calculation is completed).

help me on this