usually the first part of the barcode tells the manufacturer, and the second part tells the SKU (stock keeping unit) the manufacturer’s unique ‘part number’ for the thing being sold.

the grocer’s computer system uses these to reference its own inventory code for the thing and its current price and inventory amount etc.

from Wikipedia for SKU: SKU can also refer to a unique identifier or code, sometimes represented via a barcode for scanning and tracking, which refers to the particular stock keeping unit. These identifiers are not regulated or standardized. When a company receives items from a vendor, it has a choice of maintaining the vendor’s SKU or creating its own.[4] This makes them distinct from Global Trade Item Number (GTIN), which are standard, global tracking units. The Universal Product Code (UPC), European Article Number (EAN), and Australian Product Number (APN) are special cases of GTINs.