How it works
A SKU identifies one sellable variant: a gray eight-foot rug and a blue eight-foot rug are two SKUs. Unlike a GTIN, which is a global standard, a SKU is defined by each business, so the same physical item can carry different SKUs in a PIM, an ERP and each sales channel. Inventory, orders, pricing and cost all hang off the SKU.
Example
A brand sells the same rug on Shopify as RK-8FT-GRY, on Amazon under a seller SKU with a channel prefix, and stocks it in NetSuite under an internal item id. Margin reporting needs all three tied together.
In integrations
On the Unify Graph, the SKU is the join point between product data and finance data. The Catalog, Inventory and Orders APIs are designed to match the same item across systems by SKU, GTIN or a key you choose, with a match report that flags conflicts instead of guessing. That link is what makes margin by SKU a query. SKU mismatches are behind many commerce data problems: overselling, wrong cost of goods and margin reports that do not tie out. A reliable cross-system key is the first thing to settle in any catalog or inventory integration.