Inbound and Outbound delivery are not the same as GR and GI. Inbound is related to MM module and Outbound is related to SD module.
Inbound delivery is part of vendor confirmation and is used for optimised purchasing. It is a notification of delivery of goods from a vendor against a PO at a specific date.
Basically it denotes that the material has been shipped from the vendor's location and is in transit. In the system, Inbound is made with reference to a PO when the vendor sends his shipment notification. This Inbound is referenced while making the GR. You can control inbounds by the Confirmation Control Key(PO-->Confirmation Tab). This can be set in the Vendor master so that all POs for that vendor will be inwarded by referencing an inbound. This key can be seen/changed in the Confirmations Tab in Item Detail in ME21N. You can customize and set whether the inbounds are considered for MRP or not. The inbound dates will be helpful in planning more efficiently for the material.
The Inbound process comprises all the steps of an external procurement process that occur when the goods are received. The process is: Purchase order --> Goods Receipt, it is a follow-on activity to a purchase order. You can use VL31N transaction to create Inbound delivery & the process starts when the goods are staged at the vendoru2019s shipping point, and it ends when the ship-to party makes an acquisition posting for the goods. The goods receipt process for inbound deliveries is an essential part of the supply chain. This process includes the steps after creation of the purchase order: notification, the inbound delivery, subsequent putaway of goods, and the goods receipt posting of the ordered goods.
The outbound delivery forms the basis for goods issue posting, The data required for goods issue posting is copied from the outbound delivery into the goods issue document. You can use VL02N/VL10B/VL10C etc to create outbound delivery.
The outbound delivery supports all shipping activities including picking, packing, transportation and goods issue. When the outbound delivery is created, the shipping activities, such as picking or delivery scheduling, are initiated, and data that is generated during shipping processing is included in the delivery .