GR against inbound delivery

while going through the material of WM i have found 2 scenario for good receipt

1_)GR for inbound delivery_

If you work with deliveries, Warehouse Management activities (creating and confirming a transfer order) are completed before posting in Inventory Management. The goods receipt / goods issue posting always relates to the delivery.

2_)GR for purchase order_

However, the Inventory Management posting can also occur at the beginning of the process. The goods receipt / goods issue posting then generates a transfer requirement, which forms the basis for Warehouse Management activities in terms of planning and posting. A putaway or picking activity with a transfer order completes the process.

Could anybody tell me the importance/significance of both scenario from business point of view, i.e. when to use which GR process