What is meant by Picking Rules in Oracle APPS?

Picking Rules are created and maintained in Inventory, suggests which material to use, based on inventory controls such as Revision control, Lot control, FIFO (first in first out) or subinventory/locator picking numbers.

Picking Rule is an Item Attribute. Create a variety of picking rules and associate them with the  appropriate items. If there isn’t a Picking Rule associated with the item, the system will use the Organization’s default Picking Rule which is found on the Shipping Organization’s Parameters.