What is a UPC?
UPC (or UPC-A) means "Universal Product Number". It was created in the 70's for the UCC (Uniform Code Council), who would come to be known as GS1. It has since been re-termed "GTIN-12: Global Trade Identification Number." It refers to the bar code system used for Canada and the United States. EAN's and UPC's that come from GS1-USA are essentially identical to one another except that an EAN contains 13 digits whereas a UPC has only 12.
Below is a UPC (GTIN-12) bar code image.