LCM Setup quires Pre-Receiving

Dears,

I have just concluded making necessary SETUP, LCM as  PRE-RECEIVING

 -          Created approved PO,

-          Create LCM shipment

-          Generated Estimated cost

-          Receive the shipment

-          Invoicing matching  

-          Matches Interface Import        

-          Submit Pending Shipments

I have the following queries

1)Workbench >> Inventory Organization (selected) >> GO

2)For Shipment: Filled in OU name, Shipment Type, Receiving Location >> Create >> Shipment form is populated.

3)For Line Group: Fill in 'Group Reference' for example 'Any Reference': Source Type is 'Purchase Order'.

 

Question 1. : What is the 'Group Reference’ use used for ?

Question 2 :  Charge lines – Third party and Third party site ?

Why we need to enter this information, if enter for each Type separate Third party is accept what is the impact