I came across a posting on SDN recently with a user confused with PS Grouping and ES Grouping in payroll. This is actually very simple to use.
Personnel Subareas for Primary Wage Type (PS Grouping - table V_001P_K) allows you to give a grouping to the combination of Personnel Area and Personnel Sub Area.
Employee Subgroups for Primary Wage Type (ES Grouping - table V_503_G) similar to PS Grouping, allows you to group combination of Employee Group and Employee Sub Group.
These two grouping will be later used in a permissibility table "Define Wage Type Permissibility for each PS and ESG" (table V_511_B) The grouping value identify what position in the table V_511_B it should look at to determine permissibility.
So as you can see, if you specify the PS Grouping is 3, thus meaning in the permissibility table it should look at position 3 to find the value Blank, 1, or 2 to determine if the person is permissible to be using a particular wage type.