What is the difference between items packed individually and in case?

Amazon Seller Central will ask for your shipment’s “packaging type”: individual items or Case-packed goods.

If products in a box have different SKUs or are under different conditions, select Individual products.

If products in a box have the same SKUs and conditions and are sold as individual items, select Case-packed products. Case packs are different from multi-packs: multi-packs are marketed as collections, while products are sold individually in a case pack.

See Amazon’s Help Center for more information.