The barcode represents data in binary symbols.
These data can be read by optical reading devices, also called scanners or barcode readers, and processed electronically. The numbers below the barcode are the codes that can be read by humans. In case of problems, the code can also be entered manually.
In principle, anyone can design their own barcode, known barcodes are for example the EAN (European Article Number, including ITF and ISBN) or the target code of the post office. A 2-D code does not represent the information as lines, but as white or black pixels in an area. Even modern smartphones can now read 2-D codes.