Can this item Brother DR-630 really print 12,000 pages?
Yes it can print 12000 pages.
The drum unit is an aluminum cylinder coated with photosensitive material that clips onto the back of the toner. Drum unit is a consumable part need to replace after every 4-5 toners, when your prints appear excessively blackened, or you get a check drum warning. The drum unit does not come with a toner, so you need to buy the toner separately.