A retail barcode is a numeric code that is able to be read by an electronic device to enable faster processing of sale items through the till.
There are many different types and formats of barcodes but in the UK the retail sector generally just use two different ones EAN13 and EAN8.
EAN 13 barcodes are the most popular and EAN 8 barcodes are only issued to smaller items that would not be able to facilitate an EAN13.
The EAN13 barcode features 12 set numbers with the 13th digit being a number that checks that the 12 digits before it are correct. The only reason these numbers are shown on the base of a barcode is to make it possible for a human to read them.
The Bar code numbers are issued by the European article numbering association to insure that no barcode is duplicated on another product.
A common misconception is that the barcode contains all the information about the product, put this is not the case it is purely just a numeric code, some parts of the bar code may be generic to a manufacturer etc. but the bar code scanner or Epos system won’t know this unless told.