Basically, a thermal transfer printer is a printer which prints onto pre-cut labels, on rolls, of variable sizes, that is connected to a computer that can print variable information in the form of :
print which might indicate 'ship to' details,
'carton contents' details, 'delivery address',
'tracking' detail,
'use by' information etc. etc.
a barcode (either 1 or multiple, depending on requirements)
consequetive barcodes where each one is different from the one before or the one after it. (useful in the tracking of freight)
a single number or consequetive numbers.