Retail product label
A UPC-A or EAN-13 symbol, the product name, and often the price, sized to sit within GS1’s magnification range. This is the one case where the number has to be registered; see do you need a GS1 number. Generate one on the UPC-A generator.
Shipping carton label
Usually larger, printed directly on the box, and may combine a Code 128 tracking number with a separate ITF-14 case code. We don’t yet generate ITF-14 (see why), but Code 128 reference numbers are covered by the Code 128 generator.
Internal warehouse or asset label
Small, dense, and built for speed rather than legibility to a human. Code 128 is the standard here: no registration needed, and it packs more data into less space than the retail formats. See LPN barcode labels for the warehouse-specific version.