What is scanned at a store checkout to find the price of an item?

A barcode is a square or rectangular image consisting of a series of parallel black lines and white spaces of varying widths that can be read by a scanner. Barcodes are applied to products as a means of quick identification. They are used in retail stores as part of the purchase process, in warehouses to track inventory, and on invoices to assist in accounting, among many other uses.

Source: Shopify