Help decoding code

Can someone explain what this code is doing and how it works?

Function Grade(Bureau, Custom)
Set Table1 = Workbooks("personal.xls").Worksheets("Sheet1").Range("ScoreTableP")
RowL1 = Table1.Offset(1, 0).Resize(15, 1)
ColL1 = Table1.Offset(0, 1).Resize(1, 15)
Grade = WorksheetFunction.Index(Table1, WorksheetFunction. _
Match(Bureau, RowL1, 1) + 1, _
WorksheetFunction.Match(Custom, ColL1, 1) + 1)
End Function