Okidata label printers models are either direct thermal and/or thermal transfer. Oki direct thermal printers use special paper that reacts to heat. They do not require a ribbon of any type. They can only print in black and the printout is not as good as thermal transfer printers. These printers are good for the food industry where temps are generally cooler and for any place where the printout only needs to last 12 months or so. These printers are cheaper to buy and operate. They are also easier to load the paper as no ribbon is required.
Oki thermal transfer printers model use a carbon ribbon that actually gets transferred onto the paper due to the heat. Because they use a ribbon, the ribbon can be different colors other than just black like in Direct Thermal printers. Oki thermal transfer printers print much better than therir direct thermal printer models with crisp and durable printouts that are great for bar-codes and labels. The printouts also last much longer. You can print on paper, film and foil but the ribbon must match the material.