coding explanation

Dear Friends

Can anyone let me know what below code will do.

Item - OnPreDataItem()

IF Item.GETFILTER(“Store Filter”) <> ‘’ THEN

Item.VALIDATE(“Store Filter”);

Item.SETCURRENTKEY(“Item Category Code”,“Product Group Code”,“Vendor No.”);

LastFieldNo := FIELDNO(“No.”);

CurrReport.CREATETOTALS(Item.“Sales (Qty.)”,“Sales (LCY)”,“Disc. Amount (POS)”,“COGS (LCY)”);