A lot of people tend to make a barcode seem more complicated than it actually is. I've always considered that a barcode is a string of characters that are machine readable.
The most common barcodes, and the type that we all see when we do our shopping (remind me to tell you about my retail therapy course some time ;-) ) is known technically as linear or 1D codes typically representing up to 20 characters per code. Whilst there is no reason why a linear barcode should not encode more characters than this, I am told by my technical colleagues at Datalinx, that more than this and the size of the printable code starts to becomes too big or the thinness of the lines within the code becomes too small.
Having been around for a few years (a lady never tells you her age) and not living in a cave. I have to admit that barcodes are everywhere and not just on the food you buy in the supermarket (although that’s the place you usually notice them).
Putting a barcode on an item means it can easily be tracked and counted. Usually this is part of an automation process. The automation bit ensures that the data from the barcode is captured quickly and accurately allowing a business to be more efficient.