What is SKU?
Also known as: Stock keeping unit
A SKU (stock keeping unit) is a unique code identifying one specific sellable variant of a product — a particular size and colour, not the product family.
A red t-shirt in medium and the same shirt in large are two SKUs. Tracking at SKU level is what lets stock counts be accurate.
Keep SKU codes meaningful and stable. Renaming them later breaks the link between your historical order data and your current catalogue.